Multi-Axis Robot Brake Control via Counter-EMF Braking
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Solution Overview
Problem
Existing multi-axis robot control systems face safety concerns during emergency stops and manual movement, as the safe torque off function degrades safety when electric braking is activated, failing to meet redundancy and safety standards like ISO 10218-1 and IEC61508.
Innovation Solution
A method for controlling multi-axis robot brakes that utilizes counter-electromotive force for electric braking, with a safety system analyzing movement information to control torque cut-off and brake opening/closing, ensuring safe operation without additional electronic elements in the drives, and maintaining safety standards by monitoring movement information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the safe torque off function is deactivated to allow electric braking, then manual movement capability is improved, but safety redundancy is degraded
Solution Approach 1:
The bridge circuit is divided into two independent branches (first branch with switches S1-S3 and second branch with switches S4-S6), each capable of independently controlling torque cut-off. This segmentation allows one branch to maintain safety redundancy while the other enables electric braking functionality.
Solution Approach 2:
The control system dynamically switches between different operational states: normal operation, electric braking with one branch active, and emergency stop with both branches active. The safe torque off function is selectively deactivated only in the branch needed for braking while maintaining activation in the safety-critical branch.
2Reliability
If both branches of the bridge circuit are neutralized for safe torque cut-off, then safety redundancy is improved, but electric braking capability is lost
Solution Approach 1:
The bridge circuit control is segmented into independent branch control, allowing selective deactivation of safe torque off function in only one branch. This enables the system to maintain safety redundancy through the other branch while permitting electric braking through the deactivated branch.
Solution Approach 2:
Different safety levels are applied to different branches locally. One branch maintains full safe torque off functionality for emergency stops, while the other branch has the safe torque off function deactivated to enable electric braking operations.
3Ease of operation
If the brake is opened for manual movement, then ease of operation is improved, but uncontrolled movement risk increases
Solution Approach 1:
Before opening the brake to enable manual movement, the system preliminarily activates electric braking by deactivating the safe torque off function in one branch. This creates a counteracting force that prevents uncontrolled movement even when the brake is opened, addressing the harmful effect before it can occur.
Solution Approach 2:
The control system continuously monitors the state of the robot and provides feedback control. When the brake is opened, the electric braking system actively responds to gravity-induced movements by adjusting the short-circuited phases to maintain controlled movement, preventing the harmful effect of uncontrolled movement.
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
Enables secure manual movement and emergency stop operations while maintaining high safety levels, equivalent to double torque cut-off, by using counter-electromotive force for braking and continuous monitoring of movement information to prevent untimely torque restoration.
Implementation Method 1
The electric braking function is ensured thanks to the counter-electromotive force that the movement of the robot arm generates in the windings of the phases of the motor put short-circuited
Data Source
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AI summary
This method relates to the control of the brakes (F1, F2, F3) of the motors (M1, M2, M3) of a multi-axis robot (R1) comprising: - a robot arm (B) having at least two degrees of freedom, each associated with an electric motor (M1, M2, M3), a motion sensor (C1, C2, C3), and a brake (F1, F2, F3), - a brake interface unit (4) capable of controlling the electrical power supply to the brakes (F1-F3), - a central unit (2), - drives (V1, V2, V3) having a torque-cutting function for the motors (M1-M3), - a safety system (4, 5), the method comprising successive steps consisting of: - 6a) selecting a motor (M1-M3), - 6b) activating an electric braking function by means of the motor (M1-M3) selected, - 6c) open the brake (F1-F3), - 6d) compare the movement information delivered by the sensor (C1-C3) to a predetermined threshold,- 6e) close the brake (F1-F3) when the movement information exceeds the threshold.