Troubleshooting and Maintenance of Aerotech UNIDEX 100 Controller

Communication interruption and Host Mode malfunction

UNIDEX 100 comes standard with RS-232 communication, but the production line often shuts down due to the inability to connect to the upper computer.

1. Hardware matching between RS-232 and RS-422

If communication cannot be achieved using standard serial cables, first confirm whether the jumper on the control board matches the communication protocol. The factory default is RS-232, but if RS-422 is selected on-site for anti-interference (hardware chip needs to be customized at the time of ordering), the wiring and jumpers must be changed synchronously. In addition, when connecting to a PC, a NULL modem (crossover) cable must be used because both the controller and the PC belong to DTE devices. At the same time, it is necessary to check the baud rate setting of the upper computer software (such as com_100.exe or UT100) to ensure consistency with the baud rate (default 9600) in the controller parameter PRM: 002.

2. Service Request (SRQ) Deadlock

In Host Mode, if the controller loses response after receiving instructions from the upper computer, it is usually due to a failure of the SRQ confirmation mechanism. When the controller completes an action or encounters an error, it will send a Service Request (SRQ) to the host, and the upper computer must reply with a specific Acknowledge Code. If the upper computer program does not handle this interrupt, the controller will hang and wait, resulting in a 'crash'. When troubleshooting, the serial debugging assistant can be used to confirm whether the upper computer can correctly process and reply to the confirmation characters defined in PRM: 029.

Closed loop tuning and advanced applications of encoders

For applications that require high precision, the PID loop tuning and encoder configuration of UNIDEX 100 directly determine the machining quality of the equipment.

1. The exclusivity of encoder counters

When performing data logging or "flight output" applications, if the counter is found to be unresponsive, it is often because the encoder counter is already occupied by the system. If one of the two encoder interfaces (main port and auxiliary port) of UNIDEX 100 has been configured to provide position or velocity feedback, its internal counter chip can no longer be used for independent external event capture or comparison output. At this point, unused spare encoder ports must be allocated to auxiliary functions.

2. Manual tuning steps for PID loop without tools

If there is a lack of automatic tuning software on site, parameters can be manually adjusted through the following steps:

Clear integration terms: Set PRM: 220 (Kpos position gain) and PRM: 219 (Ki integration gain) to 0. Maintain PRM: 218 (Kp speed proportional gain) at the default of 10000.

Increase stiffness: Slowly increase PRM: 218 until the motor load feels "hardened". Note that if you hear a harsh "rustling" sound from the motor, it indicates that the gain is too high and the quantization noise is amplified. You need to adjust the value accordingly.

Introduction of integral: Increase PRM: 219 (Ki) from a small value (such as 10) until the motor can quickly stabilize in the "In Position" state without any slight creep when stopped.

Position closed loop: Finally, slowly increase the PRM to 220 (Kpos) to achieve accurate position tracking.

When tuning, a background program can be run to use the DAC() command to output the data from the speed feedback register (REG: 205) to the analog port, and observe the speed feedback waveform with an oscilloscope to determine whether the system has overshoot.