Reasons for motor torque measurement and sensor accuracy
For the test system, when it comes to test accuracy, people will definitely ask how much the system can be accurate, because everyone knows that the accuracy of the test system is affected by many factors, which is not guaranteed by the accuracy of a simple measuring instrument. Today we will talk about how the torque measurement accuracy in the motor test system is guaranteed.
In motor test systems, torque measurement is often achieved by torque sensors.
The motor under test is connected to the torque sensor through a coupling, and the other end of the torque sensor is connected to the load motor through a coupling. When the system is working, the motor under test works in the speed loop (or torque loop). The load motor works on the torque loop (or speed loop). The torque sensor measures the torque and transmits the torque value to the measuring instrument. Understand the torque test process, we can find the key factors of the torque test, first: the measurement accuracy of the torque sensor; second: the measurement accuracy of the test instrument; third: the torque loading accuracy of the motor (measured and loaded); Fourth: the mechanical installation accuracy of the system. Next we analyze each factor point.
The first is the measurement accuracy of the torque sensor. Some people say that the torque sensor is very simple, each sensor has a nominal accuracy, you can know directly by looking at the manual information. It is true that both domestic and foreign torque sensors have their nominal measurement accuracy, but torque sensors have their measurement range. How to choose the right range is also a crucial factor. Here we recommend a "three-five principle". The so-called "three-five principle" is to ensure the measurement accuracy when the test torque is within 1N.m. It is recommended that the measurement range is not less than one-third of the range, for example, the range is 1N. For sensors with .m, it is recommended to measure 0.33Nm minimum; when the measured torque is above 1N.m, to ensure measurement accuracy, it is recommended that the measurement range is not less than one-fifth of the range, such as a sensor with a range of 10N.m. 2N.m was measured. Only in this way can the measurement accuracy of the torque sensor be guaranteed.
The measurement accuracy of the second test instrument is that the traditional motor test system uses a separate instrument such as an electric parameter meter and a torque meter to measure the electrical parameters and the torque speed parameters separately. The measurement accuracy can be guaranteed in the steady state, once the transient parameters are performed. The measurement will greatly affect the measurement accuracy. Therefore, in the case of transient test, such a high-precision measuring instrument of the power analyzer must be used to synchronously measure the electrical parameters and the torque speed test to keep the measurement data accurate.
The third torque loading accuracy, when we can guarantee the measurement accuracy, we must consider the loading accuracy of the system. For example, in the test process, when we want to test the 5N.m torque point, the controller sends a command to control the motor to load. At this time, the system must be able to synchronously monitor the actual torque amount and adjust it in real time through the PID to ensure the output torque. At 5N.m (the error size depends on the degree of PID control optimization).
The mechanical installation accuracy of the fourth system and the low mechanical installation accuracy mean that the mechanical centering angle deviation of the test rig is large. When the motor test system is in long-term operation, the test gantry deformation, abnormal vibration, screw drop, and coupling will occur. Breaking and other issues. Therefore, it is necessary to ensure the accuracy of the alignment, otherwise everything that was done before will be turned into nothing.
