At present, the main equipment for measuring and evaluating the performance of motors is still the dynamometer. The initial dynamometer only measures the input voltage, current, output speed and torque of the motor, and calculates the input and output power and efficiency of the motor. However, with the rapid development of the motor industry, the number of motor testing items has been increasing, and the functions of dynamometers have also become more diverse. Even so, dynamic testing of motors remains a technical challenge within the industry.

Firstly, dynamic testing includes step response testing, analyzing the speed/torque control response time. It is the length of time it takes for the motor driver to adjust the motor back to the normal working state when the motor load changes step and the output speed/torque of the motor is altered. Generally, the speed step response time of imported  servo motors should be able to reach the microsecond level. The torque step response adjustment time should also be able to reach the ms level. Taking the Yaskawa servo motor model SGM7A-10AFA6C as an example, its speed step response time can reach 790ms, and the torque step response adjustment time can reach 28ms (the above data is provided based on the test results of the MPT1000-F motor transient control and test system of Zhiyuan Electronics).

Secondly, a speed fluctuation test is conducted to examine the fluctuation of the motor speed when the torque suddenly changes under the speed control mode. And overspeed tests are conducted to inspect the installation quality of the motor, the mechanical strength of each part of the rotor under the release force, and the mechanical strength of the bearings at overspeed.

One of the difficulties in dynamic testing of KUKA robots: Slow PID regulation

Traditional dynamometers generally use PID regulation to change the load size during the testing and loading process, and at the same time use industrial control computers for feedback control, judgment and display. Due to the delay of the communication bus, the PID regulation speed is slow, and the loading mode can only achieve loading point by point, as shown in the following figure

This leads to the inability to increase the loading speed and the inability to load any load. At the same time, due to the low sampling rate and rotational speed and torque sampling rate of the instrument itself, it greatly restricts the traditional dynamometer from being able to test the dynamic characteristics of the servo system.

The second difficulty in dynamic testing of KUKA robots

Traditional integration vendors build test platforms simply by combining instruments. Due to their lack of in-depth understanding of measurement principles and R&D experience, they find it difficult to provide comprehensive functional customization services based on customer needs. The problems thus manifested are becoming increasingly serious, such as slow loading and test response, which can only be applied to steady-state testing requirements. It supports three-channel electrical parameter measurement and analysis, but cannot achieve systematic joint debugging tests of motor drivers and motors.

With its in-depth understanding and long-term accumulation in the fields of power analysis and motor measurement, Zhiyuan Electronics has broken through the bottleneck of dynamic motor testing. By adopting an original free-loading engine and integrating the design concept of instruments, it uses a separate hardware PID controller for negative feedback control judgment, significantly enhancing the PID regulation speed. It has launched the MPT hybrid motor testing system, which is of epoch-making significance. It simultaneously meets the industry's requirements for both steady-state and dynamic measurement of motors and their control systems, leading motor experiments into the field of dynamic measurement.

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