The Influence of the Accuracy and Resolution of Servo Encoder on Servo Velocity Loop

Before we introduced the resolution and accuracy of servo motor encoders, what is the impact of resolution and accuracy on the speed loop? What is the accuracy and volatility of the speed loop? Today, we will talk to you about the relationship between the speed loop and the encoder.


In the closed-loop system, the encoder affects the performance of the control system as a feedback link.


First, response speed, accuracy and resolution


  1. Response speed: The response speed is the easiest to understand. The unresponsive encoder acts like an ideal sensor in series with a low-pass filter, which causes phase lag in the entire closed-loop control system, which affects the entire system. Stability. In most applications today, servo encoder encoder feedback is very fast and can be considered an ideal sensor. However, some serial communication encoders (SSIs) with lower communication rates inevitably cause certain delays in communication, resulting in limited bandwidth of the speed loop.

2. Accuracy: For the effect of accuracy, we first need to define the concept of speed accuracy, which is the measure of the repeatable average deviation between the actual value and the set value. The speed accuracy is illustrated in Fig. 1. It shows the overall deviation between the set value and the actual value over a period of time. Therefore, the speed accuracy can be understood as the absolute steady state error of the adjusted amount and the specified set value.

3. Stability: Although many adjustment targets involve precision, in most cases, what we want more is the “stability” of the adjustment process. This stability can be understood as the “fluctuation” of speed. Speed volatility is defined as: Volatility is an undesired actual value characteristic that is superimposed on the velocity average.


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