Position-Controlled Shaft Compensation for Elastic Lost Motion
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Solution Overview
Problem
Existing control methods for position-controlled shafts in machines fail to effectively compensate for lost motion caused by friction and elastic deformation, particularly in shafts with gears, leading to inaccuracies in position detection and movement.
Innovation Solution
A control method that uses additional target values comprising a first component dependent on the position difference, which increases monotonically with the absolute value of the position difference, and an optional second component proportional to the travel speed, to smoothly compensate for both deformation-induced and speed-induced lost motion, avoiding abrupt target value jumps and ensuring precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional target values are added to compensate for lost motion, then positioning accuracy is improved, but abrupt target value jumps occur causing control instability
Solution Approach 1:
The patent applies dynamics by making the additional target value adaptive rather than static. The compensation value dynamically adjusts based on the current position and velocity of the shaft, using a gain factor that varies with operating conditions. This dynamic approach allows smooth transitions and avoids abrupt jumps while maintaining positioning accuracy throughout the motion range.
Solution Approach 2:
The patent changes parameters by introducing a velocity-dependent gain factor and using different compensation strategies for different sections of motion. The additional target value is calculated as a function of both position and velocity parameters, allowing the system to adapt the compensation magnitude based on the current state, thereby preventing abrupt transitions.
2Ease of manufacture
If position sensors detect actuator position instead of object position, then measurement is simplified, but elastic deformation causes lost motion reducing positioning precision
Solution Approach 1:
The patent applies preliminary action by pre-calculating and adding compensation values to the target position before sending commands to the actuator. The control system proactively compensates for expected elastic deformation and friction effects by adjusting the target position in advance, rather than attempting to measure and correct the actual position after deformation occurs.
Solution Approach 2:
The patent uses feedback by continuously monitoring the actual position and velocity of the shaft and using this information to adjust the additional target value. The feedback loop allows the system to adapt the compensation in real-time based on actual operating conditions, improving positioning precision while maintaining the simplicity of actuator-based measurement.
3Speed
If friction forces are overcome to cause actual movement, then shaft movement is achieved, but energy loss occurs reducing system efficiency
Solution Approach 1:
The patent applies preliminary anti-action by incorporating friction compensation into the target position calculation. The system pre-calculates the force needed to overcome friction and includes this in the actuating signal, allowing the shaft to move more efficiently without excessive energy loss. The velocity-dependent terms in the additional target value help counteract friction effects proactively.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for effective compensation of lost motion, achieving smoother and more accurate movement of the shaft, reducing the need for additional position detection systems and improving control behavior by gradually adjusting the additional target values.
Implementation Method 1
no mechanical structure—not even a shaft of a machine tool, of a robot or another production machine—has infinite rigidity. Therefore elastic deformation occurs
Implementation Method 2
When regulating the position of shafts, generally speaking forces caused by friction occur. In order to cause an actual movement, frictional forces must be overcome
Data Source
AI summary
Control commands for a control device of a machine define a sequence of successive sections of ideal position target values for a position-controlled shaft of the machine. The ideal position target values either increase or decrease monotonically within the sections, but the direction of the monotony changes from section to section. A position controller determines actuating signals for an actuator from position target values resulting from ideal position target values, additional target values and position actual values. Within sections, the additional target values are positive (negative) when the ideal position target values increase (decrease) monotonically. The additional target values have a first component dependent exclusively on a position difference, with the magnitude of the first component increasing as the magnitude of the position difference increases, first strictly monotonically and then at least monotonically.