Servo Motor Controller Position-Dependent Gain Adjustment
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Solution Overview
Problem
In machine tools, the responsivity of servo motor controllers decreases due to variations in load on the drive axis, causing delays in reaching target positions, especially as loads increase, leading to instability and oscillation when loads are light.
Innovation Solution
A servo motor controller that adjusts the speed gain and torque offset based on the position of the driven member using a data table to optimize drive force and reduce oscillation, enhancing responsivity and stability by varying these parameters according to the load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the load acting on the drive axis is increased, then the drive force requirement is improved, but the responsivity is lowered and the feed mechanism reaches target position later
Solution Approach 1:
The patent applies dynamics by making the speed gain variable rather than constant. The speed gain is dynamically adjusted based on the position of the driven member, allowing the control system to adapt to changing load conditions. When the driven member is in positions where gravity or rotation creates higher loads, the speed gain is increased to maintain responsivity, while in positions with lower loads, the speed gain is reduced to prevent oscillation.
Solution Approach 2:
The patent changes the parameter of speed gain based on position. By storing multiple speed gain values in a lookup table and selecting the appropriate value based on the current position of the driven member, the system optimizes the balance between drive force and responsivity for different operating conditions. This parameter change allows the controller to compensate for load variations without requiring complex real-time calculations.
2Stability of the object's composition
If the load acting on the drive axis is decreased, then the oscillation is reduced, but the responsivity may be compromised
Solution Approach 1:
The control system dynamically adjusts the speed gain based on position feedback. When the driven member is in positions where gravity or rotation creates lower loads, the speed gain is automatically reduced to prevent oscillation and maintain stability. This dynamic adjustment ensures that the system remains stable across different operating conditions without sacrificing responsivity when needed.
Solution Approach 2:
The patent utilizes parameter changes by selecting different speed gain values from a stored table based on the current position. This allows the system to optimize stability by using appropriate gain values for each position, preventing oscillation during light load conditions while maintaining high responsivity when loads are heavier.
3Device complexity
If a fixed speed gain is used, then the control system is simple, but the responsivity decreases under varying load conditions
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing multiple speed gain values in a lookup table before operation. Each stored value corresponds to a specific position of the driven member, accounting for the effects of gravity and rotation at that position. During operation, the controller simply retrieves the appropriate pre-calculated value based on current position, avoiding complex real-time calculations while maintaining optimal responsivity across all positions.
Solution Approach 2:
The control system serves itself by automatically selecting the appropriate speed gain based on position feedback without requiring external intervention or complex algorithms. The pre-stored gain values enable the system to self-adjust to varying load conditions, maintaining high responsivity while keeping the control logic simple and efficient.
Data Source
AI summary
A servo motor controller includes: a servo motor; a driven member which is driven by the servo motor and in which a load acting on a drive axis is varied depending on the position of the driven member; a position detection portion and a speed detection portion for the driven member; and a motor control portion, where the motor control portion includes: a position control portion which calculates a speed command based on a positional error between a position command for the driven member and the position FB; a speed control portion which calculates a torque command by multiplying a speed error between the speed command and the speed FB by a speed gain and/or adding a torque offset to the speed error; and a change portion which changes at least one of the speed gain and the torque offset according to the position of the driven member.