Robot Arm Motor Fault Detection With Electromagnetic Joint Holding
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Solution Overview
Problem
Existing robot arm systems face challenges in detecting faults efficiently without increasing weight or space, as mechanical brakes are cumbersome and heavy, necessitating a more compact and lightweight solution for maintaining joint positions during fault assessment.
Innovation Solution
A method involving a start-up procedure for robot arm motors that includes driving the motor to a known state, testing each phase with Pulse Width Modulation signals, and applying a braking current between specific phases to maintain joint position if faults are detected, using load switches and transistors to manage power and current effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical brake is applied to each motor in the robot arm to hold the joint in position during fault assessment, then the joint position can be maintained, but the weight of the robot arm increases and space is consumed
Solution Approach 1:
The patent replaces mechanical brakes with an electrical braking system that uses the motor's own electromagnetic properties. During fault assessment, the control system applies a braking current to the motor windings, generating electromagnetic torque that holds the joint in position without requiring any mechanical brake components. This substitution eliminates the weight and space issues associated with mechanical brakes while maintaining the same functional outcome of joint position stabilization.
Solution Approach 2:
The patent enables the motor to serve its own braking function by utilizing its electromagnetic characteristics. The motor windings, which normally convert electrical energy to mechanical motion, are instead used to generate electromagnetic braking torque when a braking current is applied. This self-service approach allows the motor to maintain joint position during fault assessment without requiring separate braking components, thereby reducing overall system weight and complexity.
2Reliability
If a mechanical brake is applied to each motor to hold the joint in position, then the joint position can be maintained, but the robot arm becomes more compact in terms of space is consumed
Solution Approach 1:
The patent replaces mechanical brakes with an electrical braking system that uses the motor's own electromagnetic properties. During fault assessment, the control system applies a braking current to the motor windings, generating electromagnetic torque that holds the joint in position without requiring any mechanical brake components. This substitution eliminates the weight and space issues associated with mechanical brakes while maintaining the same functional outcome of joint position stabilization.
Solution Approach 2:
The patent makes the motor multi-functional by enabling it to perform both its primary function of driving the joint and its secondary function of providing electromagnetic braking. The same motor windings that generate motion during normal operation are used to generate braking torque during fault assessment. This multi-functionality eliminates the need for separate braking components, thereby reducing the volume occupied by the robot arm system.
3Reliability
If mechanical brakes are incorporated into the drive train of each motor, then joint position can be maintained during fault, but the device complexity increases
Solution Approach 1:
The patent replaces mechanical brakes with an electrical braking system that uses the motor's own electromagnetic properties. During fault assessment, the control system applies a braking current to the motor windings, generating electromagnetic torque that holds the joint in position without requiring any mechanical brake components. This substitution eliminates the weight and space issues associated with mechanical brakes while maintaining the same functional outcome of joint position stabilization.
Solution Approach 2:
The patent merges the braking function with the motor itself, eliminating the need for separate braking components in the drive train. The control system integrates fault detection and electrical braking control within the existing motor control architecture, combining multiple functions into a unified system. This merging reduces device complexity by removing redundant mechanical components and simplifying the overall drive train structure.
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 efficient fault detection and response in robot arm systems, maintaining joint positions against gravity while reducing weight and space requirements, enabling continuous operation and preventing drooping due to faults.
Implementation Method 1
driving a Pulse Width Modulation (PWM) signal through the motor drive circuit of the first phase of the motor
Implementation Method 2
applying a braking current between specific phases to maintain joint position if faults are detected
Data Source
AI summary
A method of testing a motor of a robot arm for a fault during a start-up procedure of the robot arm. The robot arm comprises a first link connected to a second link by a joint, the joint permitting the second link to move relative to the first link. The motor is for driving the joint and is a multiple-phase motor, each phase of the motor comprising a motor winding and a motor drive circuit for applying power to the motor winding from a power supply rail and for applying drive signals to the motor winding. The method comprises, in the following order: (i) driving the motor to a known state; (ii) connecting a first phase only of the motor to the power supply rail; (iii) driving a Pulse Width Modulation (PWM) signal through the motor drive circuit of the first phase of the motor; (iv) driving the motor to a known state; (v) with the first phase of the motor disconnected from the power supply rail, driving the PWM signal through the motor drive circuit of the first phase of the motor; and (vi) repeating steps (ii) to (v) for each of the other phases of the motor; the method further comprising, during each of steps (i) to (vi), testing whether the current from the power supply rail to the motor drive circuit exceeds a current limit.