Chapter 11 - Rotator System

11.1 Introduction

The rotator VME rack consists of two major parts:

Rotator drive motor control.

Derotator (designed for IRSPEC) drive motor control.

The adapter, mounted on the rotator, contains the guideprobes which need to rotate in order to follow the rotation of the optical field. In the case of IRSPEC, the derotator compensates for the field rotation so that the instrument does not need to rotate.

The rotator drive motor is a brushless direct drive system. Together with the associated amplifier and velocity loop, it has been manufactured by ETEL. This section contains a description of the control interface and an operating procedure.

11.1.1 References

The following are references to specific information:

Section 11.8 gives a description of the abbreviations for all the signals connected to the VME system of the rotator.

Section 11.9 is a connection list of all the computer I/O signals.

Section 11.11 provides a list of the available drawings and data sheets plus maintenance information.

11.1.2 Signal Conventions

All the signals in this Section refer to Section 11.9. As the rotators for fork arm A and B are identical, the first two characters (RA and RB respectively) are omitted in this Section.

The definition of active high and active low level signals is defined with the terms "assert" and "negate". With these terms, active high or active low is not important and has to be defined only during the signal assignment phase. Assert means: make the function logically true according to the definition in Section 11.9. Negate means: make the signal logically false.

11.1.3 Rotator Control Overview

The interface with the rotator drive system is in fact the control of the velocity loop. In principle, it is similar to the control of the AL/AZ drives. However, a complication is the use of a brushless motor which needs to be initialised and needs the value of the momentary position as well.

The interface will be described as an operating sequence; refer to Subsection 11.1.7.

11.1.4 Rotator Mechanical Integration

After mechanical integration of the motor, the rotor and stator must be electrically aligned with the encoder. This is necessary to align the motor current phase with the position output from the VME. This adjustment is valid as long as rotor, stator and encoder are not taken apart.

The following procedure is taken from ETEL documentation; however, the computer commands have been added for a full description of the sequence.

Make sure that the ETEL unit is switched OFF.

Connect motor cable to the connector named "PHASE SETTING" located on the rear panel of the ETEL unit.

On the front panel, remove the phase setting safety cover and set the sliding switch "ON".

Connect scope channel one to rear panel red pin and Gnd wire to rear panel white pin. Connect scope channel two to front panel red pin and Gnd wire to front panel blue pin.

Switch ON the ETEL SA unit; confirm the LED "phase setting" is on.

Send the following commands to the VME node:

To follow.

Turn the rotator slowly clockwise, by hand, until the AWE units are initialised (the engineering panel on the rear of the rack displays the position sent to ETEL unit). Continue turning the rotator slowly, and adjust the thumb wheel switch until both traces on the scope are in phase.

Set the sliding switch located on the front panel OFF.

Switch OFF the ETEL SA unit.

Connect motor cable to the power module located in the ETEL SA unit.

Assemble the front panel safety cover, switch ON the ETEL SA unit. The procedure is completed.

11.1.5 Rotator Gain Setting

Two 10-turn controls are provided on the front panel of the rotator control electronics: a proportional gain and an integral gain adjustment. These control the gains in the velocity loop; the gain setting is dependent upon the inertia which the motor has to drive. In case of the rotator, this is mainly determined by the type of instrument which is mounted.

The controls are provided with a 10-turn dial in order to provide a repeatable setting in case of instrument change. When they are adjusted with a certain instrument, they should not be changed any more.

The control of the velocity loop is done in board "MESURE ET - REGULATEUR DE VITESSE SE-01-AA" located in the ETEL unit. The speed information is taken from the analog output of the Heidenhain encoder head AWE 1 (the analog output of AWE 2 could also be used.

The sine and cosine signals are fed to instrumentation opamp IC 24, 25 and after rectification and linearization a DC voltage proportional to the speed is generated (test point PT2) the scaling at TP2 is 10V = 12 Deg/ sec = 2 turns/ minute.

The speed signal is on one hand fed to an OVER SPEED detector (max. 2 turns/ minute) and on the other hand summed with the computer command (TP3) after sensitivity adjustment. The scaling at TP3 is: 1LSB = 4.88mV assuming PAVHIGH is asserted.

The error signal out of IC17 goes to the PI corrector filter fitted with two dial 10-turn potentiometers (P4, P5) located on the front panel. The second order filter (IC23) is actually not connected.

11.1.6 Adjustment Procedure

The gains for no load configuration (no instrument on the rotator) are Ti (integral) = 8 and Tn (proportional) = 6. They can be used as starting points.

The procedure is as follows;

Switch the ETEL controller OFF (red push button, right of front panel).

Remove the blind plate (right side of the two front panel pots).

PT2 test point can now be accessed with a probe without removing the velocity loop card SE-01-AA (a memory scope is useful).

Switch the power ON.

Send a step input with the following sequence (assume the programs have been downloaded to the VME node);

To follow.

Slowly increase the proportional gain (Tn) up to the point where damping becomes critical (instability) then reduce it slightly.

Slowly increase integral gain (Ti) for the fastest settling (one overshoot after ramping up).

Lock the two potentiometers after final adjustment.

Switch OFF the ETEL unit.

Assemble the front panel blind plate.

The procedure is completed.

11.1.7 Rotator Operating Sequence

The operating sequence is as follows (see timing diagram CS-E-1481).

Reset.

Standby.

Initialise absolute encoder.

Send motor position.

Normal operation.

Stop.

11.1.8 Reset

Negate all output signals (PACATCH, PAAE-xx, PAPOSVAL, PAVHIGH, PAVREF-xx, PARESET, PASTINIT, PAINDIR, PAENABLE, PATREF-x). Assert signal PARESET to initialize the power amplifier electronics. Duration 1 microsec minimum.

11.1.9 Standby

Negate signal PARESET; the system is in idle state.

11.1.10 Initialise Absolute Encoder

The absolute encoder is similar to AL/AZ but has only two reading heads. In order to initialize the encoder, the axis must be rotated until an absolute reference mark is found. At this stage, rotating the motor is only possible using the signals PASTINIT and PAINDIR.

The sequence is:

To follow.

There are two possibilities:

If the error bits of the AWE's are asserted, the error status byte of the absolute encoders must be read. See the Heidenhain documentation for details.

If the error bits are not asserted, another step motion must be done. This is due to the fact that the first step of the motor after power-on is not predictable in direction and size. After the second step, the absolute encoders must be initialized or have error status.

If they are asserted, negate AEINIT, assert PAPOSVAL to indicate that the absolute encoder is initialized and start the 10 millisec reading.

After asserting PAPOSVAL, the motor electronics answers with asserting PAREADY to indicate that the motor micro controller is initialized (100 millisec timeout protection). If this signal is not asserted after this time, there is an error in the amplifier, so check PAERROR1, PAERROR2 and PAERROR3. Asserting of PAREADY by the motor electronics indicates that the drive system is ready for operation and can accept velocity commands.

The position has to be sent to the motor electronics, see next paragraph.

11.1.11 Send Motor Position

Send the position to the motor electronics using PAAE-xx (PAVREF-xx and PATREF-x should be negated still). This is a 15-bit value containing the 15 most significant bits of the calculated average of the two reading heads. The signal PACATCH is used as a strobe, the width is 6 microsec (see timing diagram CS-E-1481 for details). The scaling is: 7FFF(hex) = 0 degree, 00000(hex) = 359.989 degree. 1 lsb = 0.011 degree.

11.1.12 Normal Operation

Every 10 millisec, the momentary motor position, a velocity reference command and a torque reference command have to be sent to the motor electronics.

Sending of the position goes via PAAE-xx and sending of a velocity reference command goes via PAVREF-xx. Both data words are latched into the motor electronics by the strobe signal PACATCH. The timing requirements are the same as for the sending of the first motor position (see previous paragraph). Assertion of the signal PAVHIGH increases the speed for a given PAVREF-xx value with a factor 8. Scaling of the PAVREF is defined above.

Sending of a torque reference command goes by using PATREF-x. This is an 8 bit value and therefore it has no strobe. It is foreseen to apply torque feed forward to overcome bearing friction. There are no timing requirements of updating this byte relative to PACATCH. Scaling of the PATREF-x signal: FF (hex) = +full scale, 80(hex) = 0, 00(hex) = full scale. The torque command has not been used up to now.

11.1.13 Stop

In order to stop the motor, the following procedure has to be performed: De-celerate the motor to zero speed. Then negate PATREF-x, PAENABLE, PAPOSVAL and stop the cyclic reading of the absolute encoders.

The restart when the power is kept on is to assert PAENABLE, check ILPADIS etc, as described in Subsection 11.1.10. In this situation, the encoder units are already initialized and will not be initialized again.

When the power is switched off, the restart is from PARESET.

11.1.14Error Handling

The rotator drive is a complex system. All the error conditions can therefore not be mentioned here. But it is important to consider a few possible failure modes and the necessary software action to be taken.

11.1.15 Failure of an Absolute Encoder

The sine and cosine signals of one of the absolute encoder reading heads, are used by the motor electronics to generate the speed feedback signal. If this encoder fails, the speed feedback is missing which causes instability in the position control loop. A failure is indicated by asserting of AEERROR. It is necessary that the software, in that case, negates PAENABLE and PAPOSVAL immediately. Suggestion is to check AEERROR just before the 4 byte data transfer of each absolute encoder reading.

Note that the signal AEERROR is also used during the initialization phase of the absolute encoders. At this time, the control loops are not yet closed, and an immediate stop is not needed.

11.1.16 Power Amplifier Failure

The power amplifier has three error signals: PAERROR1, PAERROR2 and PAERROR3.

The signal PAERROR1 indicates a fatal error; the amplifier is disabled. The interlock chain will be opened so that the brake is engaged. It is necessary to negate PAENABLE in order to keep this situation.

The signal PAERROR2 indicates an overcurrent, this signal does not disable the amplifier. It is up to the operator to investigate what is the cause of this signal. The signal will be latched in the power amplifier electronics; a reset switch is provided on the front panel.

The signal PAERROR3 indicates an error between the ESO position value and the position counter in the motor electronics. The action is to stop operation immediately; negate PAENABLE.

11.1.17 Computer Failure

A computer crash will stop the cycle of updating current position, speed and torque commands to the motor electronics. The motor electronics will not take any action, except assertion of PAERROR3 if the difference in the position counters becomes too big.

A watchdog function ILWDOG is implemented which needs to be pulsed by the software. If the retrigger pulse does not come in time, the interlock chain will be opened in order to disable the amplifier and engage the brake in case of a computer crash.

11.2 ROTATOR INTERLOCKS AND LIMIT SIGNALS

11.2.1 Interlock Chain

The following description refers to diagram RO/RAINTL2.SCH.

The rotator can be moved under the following conditions:

The computer activates the "WATCH DOG" every 100ms.

The computer sends the "ENABLE" signal.

RAILCRANE is negated (crane in parking position).

RAILEMCOM is negated (no emergency stop).

RAILNEGLIM is negated (no negative limit interlock).

RAILPOSLIM is negated (no positive limit interlock).

PAERROR1 is negated (no fatal error from the amplifier).

RAILBRAKE is negated (brake is disengaged).

When all these conditions are completed RAILPADIS is negated; relay 1 is activated and ETEL driver is enabled.

11.2.2 Limit Switches

There is no limitation on rotator motion itself but on the cables rolled around. The limit switches are intended to protect them.

The following description refers to diagrams RO/LIMIT.SCH, RO/HARDLIM.SCH, RO/SOFTLIM.SCH and RO/VMERLIN.SCH.

Mechanical Switch SW1 is the positive interlock "ILPOSLIM".

Mechanical Switch SW2 is the negative interlock "ILNEGLIM".

Mechanical Switch SW3 is the direction detector. It provides two signals "POSMOV and NEGMOV", and disables the interlocks when they are not necessary as well as the next two items.

Proximity Sensor S1 is the positive limit "LSPOSLIM".

Proximity Sensor S2 is the negative limit "LSNEGLIM".

The mechanical switches are activated by the grooves made in the disc of the brake. The proximity sensors are activated by the steel profiles mounted in the inner part of the disc.

11.2.3 Interlock Function

Sheet RO/LIMIT.SCH shows the wiring and the logic function of the switches.

The principle is that interlock occurs if:

The contacts of the limit switch are open (SW1 or SW2).

The contacts of SW3 are open (respectively 11-12 and 23-24).

The flow chart shows the contact logic according to the disc rotation. It should be interpreted in the following way:

SW1 has two possible positions;

Released when its wheel falls into the hole grooved in the disc at position -90 and +270 degrees.

Activated (pushed left or right) at any other disc position.

SW2 has two possible positions;

Released when its wheel falls into the hole grooved in the disc at position +90 and -270 degrees.

Activated (pushed left or right) at any other disc position.

SW3 (direction detector) has three possible positions;

Released at position 000 degree.

Activated (pushed to left ) when going to +270 degrees.

Activated (pushed to right) when going to -270 degrees. This switch acts as a one bit memory and gives the first information about the position of the Rotator after Power ON.

1 - DISC POSITION 000 Degree

The wheel of the SW3 is just in the disc's groove; the corresponding contact code is shown in the switch's truth table in the column "MIDDLE".

Contact 13-14 closed: relay 12 is activated: (RANEGMOV negated).

Contact 21-22 closed: relay 11 is activated: (RAPOSMOV negated).

2 - DISC POSITION +90 Degree (positive move)

The wheel of SW3 has been pushed to the left,

Contact 13-14 closed: relay 12 is activated: (RANEGMOV negated).

Contact 21-22 opened: relay 11 is released : (RAPOSMOV asserted).

SW2 has detected a hole in the disc but contact 23-24 of SW3 maintains the line ILNEGLIM1 low;

Relay 3 is kept activated.

No action on the interlock; ILNEGLIM1 is kept negated.

3 - DISC POSITION +270 Degree (positive move)

SW1 has detected a hole in the disc; for this switch the wheel is released and both contacts (11-12 & 23-24) are open. As SW3 is pushed to the left contact 11-12 is open.

Relay 2 is released which causes interlock and asserts ILPOSLIM.

4 - DISC POSITION -90 Degree (negative move)

The wheel of SW3 has been pushed to the right, contact 13-14 opened: relay 12 is released: (RANEGMOV asserted).

Contact 21-22 closed: relay 11 is activated: (RAPOSMOV negated).

SW1 has detected a hole in the disc but contact 11-12 of SW3 maintains the line ILPOSLIM1 low;

Relay 2 is kept activated.

No action on the interlock; ILPOSLIM1 is kept negated.

5 - DISC POSITION -270 Degree (negative move)

SW2 has detected a hole in the disc; for this switch the wheel is released and both contacts (11-12 & 23-24) are open. As SW3 is pushed to the right contact 23-24 is open.

Relay 3 is released which causes interlock and asserts ILNEGLIM.

11.2.4 Software Limit Warnings

Proximity sensors 1, 2 also detect the +/-270 Degree position, but they give an early warning as the steel plates are 30 cm long (equivalent to +/-251 Degree). The logic function between the sensors and the direction detector is made at the relay level (diagram RO/VMERLIN.SCH).

1 - DISC POSITION 000 Degree

The wheel of the SW3 is just in the disc's groove; the corresponding contact code is shown in the switch's truth table in the column "MIDDLE"

Contact 13-14 closed: relay 12 is activated: (RANEGMOV negated).

Contact 21-22 closed: relay 11 is activated: (RAPOSMOV negated).

2 - DISC POSITION +90 Degree (positive move)

The wheel of SW3 has been pushed to the left,

Contact 13-14 closed: relay 12 is activated: (RANEGMOV negated).

Contact 21-22 opened: relay 11 is released : (RAPOSMOV asserted).

SENSOR 2 detects the steel profile; relay 14 is activated, but Relay 12 is also activated (RANEGMOV negated), thus RALSNEGLIM is kept negated.

3 - DISC POSITION +251 Degree (positive move)

Sensor 1 detects the steel profile; relay 13 is activated, Relay 11 is released (RAPOSMOV asserted) thus RALSPOSLIM is asserted.

4 - DISC POSITION -90 Degree (negative move)

The wheel of SW3 has been pushed to the right.

Contact 13-14 opened: relay 12 is released : (RANEGMOV asserted).

Contact 21-22 closed: relay 11 is activated: (RAPOSMOV negated).

SENSOR 1 detects the steel profile; relay 13 is activated, but Relay 11 is also activated (RAPOSMOV negated) thus RALSPOSLIM is kept negated.

5 - DISC POSITION -251 Degree (negative move)

Sensor 2 detects the steel profile; relay 14 is activated, Relay 12 is released (RANEGMOV asserted) thus RALSNEGLIM is asserted.

11.2.5 Mechanical Adjustment

The rotator amplifier should be disabled, and the brake disengaged; for this the switch "BRAKE MANUAL" is provided on the front panel of the brake amplifier.

Adjustment should be done at rotator zero position when the wheel of the SW3 (direction detector) comes just in the groove of the disc. SW3 is released, and a gap of 1mm is left between the wheel and the edge of the disc.

The mechanical switches SW1, SW2 must be activated (direction is not important).

Turn the rotator by hand +/-90 Degree and check that:

The wheel of SW3 is nicely pushed left or right and runs along the edge of the disc.

The wheels of SW1, SW2 correctly fall into the holes grooved in the disc. The arm supporting the wheel should not touch the disc.

The proximity sensor 1 is activated by the high steel profile (this plate is mounted at position +251 Degree). It should be adjusted 1 to 2mm distance to the steel plate.

The proximity sensor 2 is activated by the low steel profile; (this plate is mounted at position -251 Degree and 3mm spacers are added to have a different depth relative to the other plate). The sensor 2 is 1 to 2mm away from the low profile and 4 to 5mm away from the other profile thus insensitive to it.

 

11.3 MOTOR

11.3.1 Motor Cable

As the output stage of the amplifier has a very fast switching time, a too high capacitive load leads to overcurrent. The maximum admissible stray capacitance for the power cable is therefore 500 pF. The actual cable is 10 meters long and has 43 pF/m between each wire and the shield. This has been achieved by inserting 4 high voltage wires in the centre of a flexible metallic pipe with a diameter of 50 mm.

Wire type : CERN No 04.08.61.129.0.

Rotator B is connected with one coaxial cable RG62 per motor phase.

11.3.2 Cooling System

It is not planned to use this. During the test no significant heat dissipation was detected.

A PT1000 is included in the winding for temperature survey but for the first rotator the sensor seems to be broken. There is no possibility of replacing it.

11.4 BRAKE

Type 450SE from Firm ATV.

A spring loaded screw has been added at the side of the brake in order to ensure a friction-free disk after disengaging the brake.

The specified braking torque (1000 N) is obtained when the total space between disc and brake pads is less than 0.7mm (brake being disengaged). This value includes ALL errors such as disk wobbling, centering and parallelism with pads.

Make sure that the total wobbling of the disc is +/-0.2mm

See Brake Adjustment Brochure

11.5 ENCODER

11.5.1 Electronic

Type AWE 1024 Identification number 231 211 02.

They are similar to ALTAZ type, but an output has been added by Heidenhain for sine cosine analog output. (P2 connector). P2 of AWE1 is connected to ETEL electronics for SPEED signal generation. AWE 2 is identical (but P2 is not conected) and can be a spare for AWE1. If AWE1 fails, exchange AWE1 and AWE2, and fit a normal AWE1024 in the AWE2 position.

The phase setting of the ETEL electronics remains the same as there is no mechanical change at encoder head No. 1.

11.5.2 Adjustment

The maximum wobbling between disc and heads must be no more than 0.02mm. Desc eccentricity must be less than +/- 75 micro-metre. The reading heads must be mounted exactly radially; this can be checked by observing the sine and cosine waves on an oscilloscope - the amplitude level must be no more than 3V peak to peak.

The method of measuring wobble is the same as for EXE 702 (refer to Subsection 11.12.2).

11.6 ROTATOR DRIVER (ETEL)

Full documentation is provided by ETEL. The following spares are available:

Qty 1, Microprocessor Board
Qty 2, Velocity Loop Boards
Qty 1, Power Supply Survey
Qty 1, Power Supply Block with Transformer

11.7 WATCHDOG

A relay contact is included in the interlock chain and kept closed as long as the computer sends a pulse every second (duty cycle 50%).

If, for any reason, the computer fails, the contacts open after an adjustable time period - normally set at 4 seconds.

The relay is manufactured by Weidmuller, type EGM/A 24V 11 760.6 (modified). The modificatio is an RC circuit at the pulse input to obtain adequate edge sensitivity; an "X" on the programming side indicates this modification is included.

Relay setting - 0 1 0 0.

11.8SIGNAL DESCRIPTIONS

The signals in the rotator subsystem are divided into the following groups that indicate where the signals originate (inputs to the computer), or where they have to be routed (outputs from the computer).

PA: Power amplifier signals
AE: Absolute encoder signals
LS: Limit switch signals
IL: Interlock signals
DR: De-rotator signals
xx: Miscellaneous signals (where "xx" is not any of the previous)

The above abbreviations are used as the second prefix after the standard prefix RA or RB for the rotator system on Fork Arm A or B respectively. As both systems are the same, from an electro-mechanical perspective, all signals in this section are defined for Fork Arm A.

The de-rotator (designed for IRSPEC) is not described in this document.

11.8.1 Power Amplifier Signals

NAME	TYPE	DESCRIPTION
RAPAENABLE*	DO*1	Disengage brake and enable power amplifier
RAPAE2RES*	DO*1	Reset power amplifier error status latch
RAPAERROR1*	DI*1	Over-temperature, too high speed, PS fail: power amplifier disabled (fatal error)
RAPAERROR2*	DI*1	Over-current (non-fatal error)
RAPAERROR3*	DI*1	Discrepancy between ESO and ETEL absolute position (non-fatal error)
RAPACATCH*	DO*1	Strobe for ETEL electronics
RAPAAExx*	DO*15	Average value for AE head 1 and 2. xx = 24 (msb) through 10
RAPAPOSVAL*	DO*1	Absolute position data is valid
RAPAREADY*	DI*1	Motor micro-controller is initialised
RAPAVHIGH*	DO*1	Velocity in high speed mode
RAPAVREFxx*	DO*12	Velocity reference, xx = 11 (msb) through 00
RAPARESET*	DO*1	Reset motor power electronics
RAPASTINIT*	DO*1	Move motor one step
RAPAINDIR*	DO*1	Step direction
RAPATREFx*	DO*8	Motor torque reference, x = 8 (msb) through 0

11.8.2 Absolute Encoder Signals

The rotator absolute encoder system consists of the same components as the altitude and azimuth encoders. The difference is that for the rotator, two reading heads are used instead of four. With two reading heads, the required accuracy can be obtained. Therefore, the I/O signals are the same as for AL/ AZ but only for two heads.

11.8.3 Limit Switch Signals

NAME	TYPE	DESCRIPTION
RALSPOSLIM	DI*1	Positive limit detected
RALSNEGLIM	DI*1	Negative limit detected

11.8.4 Interlock Signals

NAME	TYPE	DESCRIPTION
RAILPADIS	DI*1	Power amplifier is disabled
RAILPOSLIM1	DI*1	Positive interlock limit 1 detected, amplifier switched off
RAILNEGLIM1	DI*1	Negative interlock limit 1 detected, amplifier switched off
		Note: Interlocks 1 are generated by the rotator
RAILPOSLIM2	DI*1	Positive interlock limit 2 detected, amplifier switched off
RAILNEGLIM2	DI*1	Negative interlock limit 2 detected, amplifier switched off
		Note: Interlocks 2 are generated by the cable
RAILBRAKE	DI*1	Brake is dis-engaged
RAILBRMAN	DI*1	Manual drive, amplifier disabled, brake dis-engaged
RAILEMSTO	DI*1	RA emergency stop button pressed, amplifier switched off
RAILEMCOM	DI*1	Any emergency stop button pressed, amplifier switched off
RAILWDOG	DO*1	Watch dog pulse signal
RAILCRAN	DI*1	Crane is in operating area, amplifier switched off

11.8.5 Derotator Signals

NAME	TYPE	DESCRIPTION
RADRxxyyy		Derotator signals

11.8.6 Miscellaneous Signals

NAME	TYPE	DESCRIPTION
RAPWOFF*	DO*1	Rotator switched power off
RAPOSMOV*	DI*1	Rotator angle is positive (between -15 and +270 degrees)
RANEGMOV*	DI*1	Rotator angle is negative (between -270 and +15 degrees)
RASYNC*	DI*1	Clock synchronisation

 

11.9 CONNECTION SCHEDULE

This signal schedule describes the location of the VME computer signals for the rotator system.

The signals are explained in Section 11.8.

This section provides the information to track each signal from the software driver to the input or output of the VME board.

The VME computer for the rotator system contains 2 digital I/O interface boards for the rotator, and the boards required for the derotator (if the derotator is mounted).

The digital signals are connected via flat cable to the Weidmuller multi-termination strips MTS1 through MTS4.

11.9.1 Power Amplifier Signals 1

SIGNAL	PORT	I/O	PIN	S/W PORT	S/W BIT	MTS1
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____

11.9.2 Power Amplifier Signals 2

SIGNAL	PORT	I/O	PIN	S/W PORT	S/W BIT	MTS2
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____

 

11.9.3 Absolute Encoder Signals

SIGNAL	PORT	I/O	PIN	S/W PORT	S/W BIT	MTS3
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____

11.9.4 Interlock and Limit Signals

SIGNAL	PORT	I/O	PIN	S/W PORT	S/W BIT	MTS4
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____
__________	_____	_____	_____	_____	_____	_____

 

11.10 SERVO ADJUSTMENT

The gain adjustment of the NTT Rotator must be performed in two steps:

Adjust the velocity loop.

Adjust the position loop.

The gain settings depend on the dynamic performance and requirements of the instrument that is mounted, and they must, therefore, be adjusted at each instrument change.

11.10.1 Velocity Loop

The velocity loop has two adjustment potentiometers with 10-turn dials for the prortional and integral gain. The adjustment must be done when the optical instrument is mounted.

When no instrument is mounted, as in the case of IRSPEC, the adjustment can be done as described below - but without open-loop measurements.

With an instrument mounted, the technician must check if open-loop measurements are necessary. With EMMI (which is a mechanically "stiff" instrument, the same procedure can be used.

The procedure is as follows:

Remove the D/A speed converter device on the ETEL Analog Board.

Bypass the PI integrator capacitor with a jumper wire.

Turn the proportional gain (Tn) low, and set potentiometer Ti to 80%.

Connect an analog speed command to the speed command test-point (made possible by the removal of the D/A converter).

Adjust the proportional gain and measure the small signal bandwidth by using a frequency analyser.

Calculate the integrator capacitor required (using a PI take-over frequency of 1/10 of the proportional bandwidth) and install on the board; remove the jumper wire.

Verify the dynamic performance. If necessary, fine adjustment can be made with the Tn and Ti potentiometers.

Verify that the loop is stable for all speeds. Experience has shown that the loop tends towards instability at high clockwise speeds, but not in the counter-clockwise direction. The exact reason for this is not yet known.

Remove the analog speed command input, and refit the D/A speed converter device.

11.10.2 Position Loop

The adjustment of the position loop is more complicated than the velocity loop as it depends on many more variables. This is because the gain settings are not all independent of each other, and are switched when the target position is approached.

Firstly, the gain for small steps must be adjusted, then the gain-switching parameters are set, followed by the gain for large steps. Finally, the parameters are optimised for the best overall performance.

Adjustment of Gains for Small Steps

Check the speed scaling.

Calculate a start value for the proportional gain using the result of the velocity loop measurements. A typical value is a proportional gain such that the closed loop bandwidth is approximately 30% of the velocity loop bandwidth.

Set the integral gain to a very low value.

Make a small step response of approximately 20 arcseconds. There should be no acceleration limit active.

Note: A test-point can be the velocity command test-point on the ETEL Analog Board. It is best to use a program to display the position error.

Slowly increase the proportional gain for optimum step response.

Calculate the small signal bandwidth.

Calculate a start value for the integral gain using a PI take-over frequency of 1/10 of the bandwidth.

Using this value as a starting point, optimise the integral gain.

Adjustment of Gain Switching Parameters

When a target position is approached, the high gains described above are switched on. This switching limit has to be set such that there will never be an acceleration limitation when these gains are switched on.

Practical values are 100 arcseconds for the TPERR value and 80 arcseconds for the PTERR.

Adjustment of Gains for Large Steps

The large-step response is determined by the parameters of maximum acceleration, maximum speed and a gain value (CTLOW) for large steps.

The first two values are determined by the specification, while the last is the implementation of the braking phase from the motion speed (any value from 0 to maximum speed) to the zero speed using maximum de-acceleration. This is done using the square root of the position error.

Final Adjustment

The final adjustment has to be made by checking the low speed tracking performance. The experience is that a reduced integral gain of the position PI controller results in smaller limit cycles. However, it also results in a larger tracking error at high acceleration.

The present values are:

PARAMETER	WITH IRSPEC INSTRUMENTATION	WITH EMMI INSTRUMENTATION
Velocity loop Kp	40%	90%
Velocity loop Ki	40%	40%
Velocity loop integrator capacitor	1 microFarad	3.2 microFarad
Position loop Kp	0.1	0.06
Position loop Ki	0.1	0.002
Position loop CTLOW	1.4
Track to preset error	2600 (100 arcseconds)
Preset to track error	2070 (80 arcseconds)
Acceleration limit	21 (0.3 deg/sec2
Maximum speed	2000 (3 deg/sec

 

11.11 MAINTENANCE INFORMATION

This section lists the maintenance information for the NTT Rotator electronic systems.

11.11.1Drawing List

TITLE/ SUB-TITLE	SHT NUMBER	LAST UPDATE	DRAWING NUMBER
Timing Diagram	1	21-09-89	CS-E-1481
Flow Chart	1&2	23-09-89	CS-E-1686
Rotator Control	5		CS-E-1628
- Limit Detection	1/5	13-01-89
- VME Input/ Output	2/5	24-01-89
- Hardware Limits	3/5	12-03-90	HARDLIM.SCH
- Software Limits	4/5	12-03-90	SOFTLIM.SCH
- Limit Detection and Interlock	5/5	21-02-90	LIMIT.SCH
Rotator B Interlock Chain	1	23-07-90	RAINTL2.SCH
Rotator A Interlock Wiring Diagram	1	12-03-90	RAINTL1.SCH
Rotator B Interlock Wiring Diagram	1	23-07-90	RBINTL1.SCH
VME Digital Inputs with Relays	1	23-07-90	VMERLIN.SCH
Brake Control Chassis	1	12-03-90	BRAKEAMP.SCH
Rotator TS Connections	1	17-05-90	TSCON.SCH
Rotator Motor Connections	1	12-03-90	MOTCON.SCH
ESO/ETEL Connections	2
- to Connector VME ESO	1/2	20-03-90	RADESET1.SCH
- to Connector J ESO	2/2	20-03-90	RADESET2.SCH
Analog Encoder Input to ETEL Amplifier	1	12-03-90	ANSINCOS.SCH
Rotator Interconnections	1	17-05-90	INTERCON.SCH
AWE to Computer Connections	1	19-08-88	CS-E-1555
Power Line Distribution	1	12-03-90	POWERDIST.SCH
Time Distributor Interface	1	12-03-90	TIMEDIST.SCH
Motor Temperature Display	1	12-03-90	TEMPDIST.SCH
Display Panel Driver Control	1	12-03- 90	DISPLAY.SCH
Layout	2		CS-E-1559
- Rack Layout	1/2	12-12-88
- Absolute Encoder Cabling	2/2	24-11-88
VME Chassis Layout	1	08-08-88

11.11.2 Data Sheets

DESCRIPTION	NO. OF SHEETS
Heidenhain ERO7001	32
Heidenhain EXE702	4
BRAKE ATV Notice de Montage & Reglage	11
- Diagram	1

11.11.3 Speed Control Documentation

Separate documentation from:

ETEL SA,
Zone Industrielle,
CH-2112 Motier,
Switzerland