Servo Controller Torque Limiting for Gravity Axis Drop Reduction
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Solution Overview
Problem
Existing servo controllers fail to effectively reduce the amount of dropping of a gravity axis during braking, leading to inaccuracies and vibrations in machine tools and industrial machines due to the sudden transition from motor control to mechanical brake, which results in excessive drop distances.
Innovation Solution
A servo controller with a torque limiting value generating part that gradually reduces the torque command value from a first value larger than the gravity force to a second value smaller than the gravity force after activating the mechanical brake, thereby controlling the position of the servomotor and limiting the drop distance within the backlash width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gravity axis is previously lifted by a distance larger than the amount of dropping before the mechanical brake is activated, then the gravity axis can be prevented from dropping, but the device complexity and operation complexity increase
Solution Approach 1:
The invention changes the torque parameter dynamically during braking by continuously reducing the torque limiting value from a first value (larger than gravity force torque) to a second value (smaller than gravity force torque). This parameter change allows the mechanical brake to engage smoothly without causing the gravity axis to drop, eliminating the need for complex preliminary lifting mechanisms while maintaining reliability.
2Speed
If the torque command value is suddenly reduced when switching from motor control to mechanical brake, then the braking response is fast, but the gravity axis drops by a large distance causing vibration and noise
Solution Approach 1:
The invention applies dynamics by continuously changing the torque limiting value during the braking process rather than maintaining a fixed value. The torque limiting value is dynamically reduced from a first value to a second value after brake activation, which allows the braking response to remain fast while preventing sudden position changes that would cause vibration and noise, thus maintaining positioning accuracy.
3Stability of the object's composition
If the torque limiting value is maintained at a high value during braking, then the gravity axis position is stable, but the braking effectiveness is reduced and stopping distance increases
Solution Approach 1:
The invention uses periodic action by continuously reducing the torque limiting value in a controlled manner after brake activation. This continuous reduction creates a time-based sequence where the torque limiting value transitions from a first value to a second value, maintaining position stability initially while progressively increasing braking effectiveness, thus achieving both stability and timely stopping.
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 solution reduces the drop velocity and distance of the gravity axis, minimizing noise and vibration, and enhancing the operational accuracy of machine tools and industrial machines by maintaining the position within the backlash width during braking.
Implementation Method 1
a mechanical brake with a backlash for holding the gravity axis
Implementation Method 2
a servo controller for controlling a servomotor which drives a gravity axis
Implementation Method 3
the gravity axis may fall by gravity when power to the servomotor is shut
Data Source
AI summary
A servo controller having a function for reducing an amount of dropping of a gravity axis provided with a machine. The Servo controller is configured to control a servomotor for driving a gravity axis of the machine, and includes a brake signal outputting part configured to output a brake activation signal and a brake release signal to a mechanical brake for holding the gravity axis; a torque command generating part which generates a torque command value for controlling the position of the servomotor; and a torque limiting value generating part which generates a torque limiting value for limiting the torque command value. The torque limiting value generating part continuously reduces the torque limiting value from a first value larger than a torque corresponding to the gravity force to a second value smaller than the torque corresponding to the gravity force, after the brake activation signal is output.