Servomotor Position Compensation Oscillation Control
Solution Overview
Problem
Existing servomotor control devices experience oscillation in position compensation due to drive force estimates unrelated to mechanical operation, leading to reduced precision during stop or low-velocity operations.
Innovation Solution
A servomotor control device with a position command compensation unit that includes a restriction part to limit updating of the compensation amount when command acceleration or velocity is below a desired value, and optionally uses filters to smooth changes in the compensation amount, preventing oscillation by controlling the servomotor with restricted position command values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position compensation is continuously updated based on drive force estimation, then position control precision is improved, but oscillation occurs in the compensation amount during stop or low-velocity operations
Solution Approach 1:
The system dynamically adjusts the updating behavior of the compensation amount based on real-time operating conditions (command velocity and command acceleration). When command velocity exceeds a first threshold or command acceleration exceeds a second threshold, the compensation amount is updated normally. When both thresholds are not exceeded, updating is restricted. This dynamic adaptation resolves the contradiction by allowing continuous updating during active operations for precision while preventing oscillation during stop or low-velocity conditions.
Solution Approach 2:
The system changes the parameter of compensation amount updating based on operating conditions. By monitoring command velocity and command acceleration parameters, the system switches between two modes: normal updating mode (when velocity > first threshold or acceleration > second threshold) and restricted updating mode (when velocity ≤ first threshold and acceleration ≤ second threshold). This parameter-based control resolves the contradiction between precision and stability.
2Manufacturing precision
If the compensation amount is updated based on drive force during low-velocity operations, then position accuracy is maintained, but oscillation and instability arise
Solution Approach 1:
The system implements dynamic control of compensation updating by continuously monitoring command velocity and command acceleration. During low-velocity operations (command velocity ≤ first threshold and command acceleration ≤ second threshold), the system dynamically switches to restricted updating mode, preventing the oscillation that would otherwise occur. During normal operations, full updating is enabled to maintain position accuracy. This dynamic behavior resolves the contradiction between maintaining accuracy and ensuring stability.
Solution Approach 2:
The system takes preliminary anti-action by predicting when oscillation might occur based on command velocity and acceleration thresholds. Before oscillation can occur during stop or low-velocity operations, the system preemptively restricts the updating of the compensation amount. This prevents the harmful oscillation before it starts, while still allowing normal updating during conditions where it would be beneficial.
Data Source
AI summary
A servomotor control device includes a servomotor; a driven body configured to be driven by the servomotor; a connection mechanism configured to connect the servomotor and driven body, and transmit power of the servomotor to the driven body; a position command generation unit configured to generate a position command value; a motor control unit configured to control the servomotor using the position command value; a position command compensation unit including a force estimation part configured to estimate a drive force acting on the driven body at the connection mechanism, and a compensation amount generation part configured to generate a compensation amount for compensating the position command value based on the estimated drive force; and a restriction part configured to restricting updating of the compensation amount when a command acceleration or a command velocity of the position command value is no more than a desired value.