TRACE Quadrant Selector Documentation OPERATION: The Quadrant Selector electronics is a slightly modified version of the MDI shutter/PA wheel electronics. The main difference from the PA wheel is that Quadrant Selector electronics holds on power for a short time after a move has been made, forcing the motor to the proper position. This is necessary because the motor does not have nearly enough magnetic detent to keep the blade in the proper position unless the blade is stopped when power is taken away. COMMANDS: 0 Nothing 1 Move CW 2 Reset 3 Move CCW 4 Load Stopping Position 5 Read Encoder 6 Nothing 7 Nothing A CW move increases the encoder reading. CW and CCW refer to rotation viewed looking at the encoder end of the motor. RESET SEQUENCE: When power is first applied to the Quadrant Selector it must go through a reset sequence before it is ready to be used. The recommended sequence is: 1) Send Reset (encoder reads 63) 2) Load Stopping Position 33 (34 if cold) 3) Move CW (this leaves it in the 147/148 position). In normal operation the Quadrant Selector moves to one of 4 positions. The following table shows how to move from a position to any other. For example to move from position 1/2 to 74/75, first load a stopping position of 4, then send a CW command. A 180 degree move can be made either CW or CCW. This table arbitrarily shows 2 CW and 2 CCW 180 degree moves. When the motor comes to a stop its position is nominally at an encoder transition, therefore a given motor position is defined by the 2 possible encoder readings. +-------------------------------------------------+ | Present | Desired Position | | Encoder +---------+---------+---------+---------| | Reading | 1/2 | 74/75 | 147/148 | 220/221 | |=================================================| | 1/2 | - | 4,CW | 72,CW | 35,CCW | |---------+---------+---------+---------+---------| | 74/75 | 72,CCW | - | 77,CW | 145,CW | |---------+---------+---------+---------+---------| | 147/148 | 77,CCW | 145,CCW | - | 150,CW | |---------+---------+---------+---------+---------| | 220/221 | 223,CW | 150,CCW | 218,CCW | - | +-------------------------------------------------+ COUNTER SEQUENCE: The counter counts in kind of a funny sequence. The counter is 8 bits. The lower 6 bits count 0 to 35, the top 2 bits define which quadrant the blade is in. If all 8 bits are included the sequence is: 0 to 5, 70 to 78, 143 to 151, 216 to 224, 33, 34, 35. See drawing TRA-031073. The motor may be spun continuously by loading in a stopping position that is not part of the counting sequence, 111 for example. Inertia: .077 oz-in sec^2 (calculated) Mass: 600 g, (prototype measurement, 475 motor, 125 blade assy.) Motor resistance: 24 Ohms (prototype measurement) Disturbance Torque: 22 oz-in peak (calculated) Motor: Inland Motor P/N RB-01501-R02 12 pole 3 phase brushless DC motor Measured performance (prototype motor): Calculated Resistance: 27.78 Ohms Damping: .03971 oz-in / rad/sec BEMF: .34844 V / rad/sec Torque Constant: 49.34 oz-in / Amp Motor Constant: 9.361 oz-in / W Prototype Measurements (15.0 V): Move Time to Position Time to Done Energy to Move ------------------------------------------------------------------------- 90 deg. 0.32 s 1.08 s 7.8 J 180 deg. 0.42 s 1.19 s 7.8 J RESET 1.22 s 11.4 J 33 CW (after reset) 1.55 s 15 V: .6 A for .8 s (90 or 180 degree move). Nearly all this power is dissipated in the motor's windings. The prototype has been demonstrated to operate acceptably on voltages from 13 to 17 Volts. But in order to do so the reset sequence needs to be adjusted. For lower voltages a higher number must be loaded. For instance to operate on 13 volts a 35 CW should be sent after the reset. You'll know you need to use a different number if after a reset sequence the encoder doesn't read 147/148. View looking Quadrant | Wavelength | Encoder into TRACE: ----------+----------------+--------- A | 171 Angstroms | 220/221 GT B | UV | 147/148 A | B C | 195 Angstroms | 74/75 ----+---- D | 284 Angstroms | 1/2 D | C Connector | Backplane ------------+------------- J350-A | 40 J350-B | 41 J350-C | 42 J350-D | NC | J351-A | 35 J351-B | 36 J351-C | 37 J351-D | 34 | J352-A | Thermistor J352-B | Thermistor J352-C | 39 J352-D | 38 OPERATION BY THE CONTROL COMPUTER: In order to keep people less confused the CC accepts numbers from 0 to 36 and maps them to the strange sequence before actually sending them to the QS. The numbers 0 thru 35 cause the QS to stop in various positions, the number 36 causes the QS to spin. +-----------------------------------------------------------+ | | Present | Desired Position | | Present | Encoder +---------------------------------------| | Position| Reading | A | B | C | D | |===========================================================| | A | 28/29 | - | 26,CC | 22,CC | 31,CW | |---------+---------+---------+---------+---------+---------| | B | 19/20 | 22,CW | - | 17,CC | 13,CC | |---------+---------+---------+---------+---------+---------| | C | 10/11 | 17,CW | 13,CW | - | 8,CC | |---------+---------+---------+---------+---------+---------| | D | 1/2 | 35,CC | 8,CW | 4,CW | - | +-----------------------------------------------------------+ MNEMONICS: ikqsenc - all 8 bits of the encoder ikqspos - lower 6 bits of the encoder (reads 0-35, 63 after reset) ikqsnum - top 2 bits of the encoder (A=3, B=2, C-1, D=0)