Robot Arm Motor Phase Fault Detection With Electrical Braking
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Solution Overview
Problem
Existing robot arm systems face challenges in detecting and responding to faults efficiently, particularly in terms of weight and space, as mechanical brakes are often used to hold the arm in position during fault assessment.
Innovation Solution
A method is introduced that involves testing each phase of the motor by comparing the voltage supplied to the winding with high and low thresholds during PWM signals, and applying a braking current between specific pairs of motor phases to maintain joint position against gravity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical brakes are incorporated into each motor of the robot arm to hold the arm in position during fault assessment, then the robot arm can maintain its position reliably, but the weight and space requirements of the robot arm increase
Solution Approach 1:
The patent replaces mechanical brake systems with an electrical braking mechanism. The motor controller applies a braking current to the motor windings to generate electromagnetic torque that holds the robot arm in position during faults, eliminating the need for mechanical brakes and their associated weight and space requirements
Solution Approach 2:
The patent changes the operational parameters of the motor by applying controlled current during fault conditions. By adjusting the current magnitude and direction through the motor windings, the system generates the necessary holding torque without mechanical components, dynamically adapting the motor's function from motion generation to position holding
2Reliability
If mechanical brakes are incorporated into each motor of the robot arm to hold the arm in position during fault assessment, then the robot arm can maintain its position reliably, but the space occupied within the robot arm increases
Solution Approach 1:
The patent replaces mechanical brake systems with an electrical braking mechanism. The motor controller applies a braking current to the motor windings to generate electromagnetic torque that holds the robot arm in position during faults, eliminating the need for mechanical brakes and their associated weight and space requirements
Solution Approach 2:
The patent makes the motor serve multiple functions: during normal operation it generates motion, and during fault conditions it generates holding torque through electrical braking. This multi-functionality eliminates the need for separate mechanical brake components, reducing the space occupied within the robot arm
3Measurement precision
If voltage threshold testing is performed during PWM signals to detect faults, then fault detection precision is improved, but the complexity of the control system increases
Solution Approach 1:
The patent implements feedback by continuously monitoring the voltage supplied to motor windings during PWM operation and comparing it against predetermined thresholds. This feedback mechanism enables automatic fault detection when voltage deviates from expected ranges, improving detection precision through systematic voltage measurement and comparison
Solution Approach 2:
The patent monitors changes in voltage parameters during motor operation. By detecting voltage deviations from predetermined thresholds during PWM cycles, the system identifies faults through parameter changes, achieving precise fault detection through electrical parameter analysis rather than complex mechanical sensing
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 without the need for mechanical brakes, reducing weight and space requirements while effectively maintaining the robot arm's position during faults.
Implementation Method 1
The motor drive circuit applies a PWM signal to a motor winding of the motor phase
Implementation Method 2
turning on the low side transistor of every phase of the motor
Implementation Method 3
testing whether the voltage supplied to the motor winding of the first phase of the motor differs from each of the power supply rail voltage and ground by more than respective values
Data Source
Figure 1~2
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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.