Prosthesis Motor Control for Gripping Force via Periodic Pulses
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Solution Overview
Problem
Prosthetic hands with motor-driven digits face limitations in achieving sufficient gripping force, especially when the motor is constrained in size and motive power, and existing methods only offer a moderate increase in force.
Innovation Solution
A method involving a motor-controlled prosthesis that determines when movement is arrested against a surface and provides specific driving electrical pulses to increase the gripping force, utilizing techniques such as current threshold detection and pulse width modulation to enhance the motor's output, allowing for a significant increase in gripping force up to 3.5 kg.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the motor size is constrained to fit within the prosthesis digit, then the prosthesis becomes more compact and wearable, but the gripping force is limited
Solution Approach 1:
The system applies periodic electrical pulses to the motor instead of continuous power. The control circuit detects when movement is arrested (component bears against surface) and provides driving electrical pulses at that moment, creating a periodic action that significantly increases gripping force (from 1 kg to 3.5 kg) without requiring a larger motor.
2Force
If the motor motive power is increased to achieve greater gripping force, then the gripping capability improves, but the motor size and power consumption increase
Solution Approach 1:
The control circuit performs preliminary detection to determine when movement is arrested before applying the driving electrical pulses. This preliminary action allows the system to apply motor power at the optimal moment (when the component bears against the surface), achieving high gripping force with minimal power consumption from a small motor.
Solution Approach 2:
By applying electrical pulses periodically only when movement is arrested rather than continuously, the system achieves high peak gripping force (3.5 kg) while maintaining low average power consumption, resolving the contradiction between force and power requirements.
3Speed
If continuous electrical power is supplied to the motor, then the component moves smoothly, but the gripping force when bearing against surface is insufficient
Solution Approach 1:
The system transitions from continuous power supply to periodic pulsing. Electrical pulses are provided specifically when movement is arrested (detected by the control circuit), delivering concentrated force during the gripping phase while maintaining smooth movement during the approach phase, thereby resolving the contradiction between smooth movement and gripping force.
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 method effectively increases the gripping force of a prosthesis digit by a considerable amount, from 1 kg to up to 3.5 kg, even when the motor is constrained, making it suitable for applications where size and motive power are limited.
Implementation Method 1
moving the component by means of a motor
Implementation Method 2
determining when movement of the component is arrested by measuring an electrical signal passing through the motor
Data Source
AI summary
The present invention relates to a method of controlling a movable component of a prosthesis or orthosis. The method (100) comprises moving the component by means of a motor (102) and determining when movement of the component is arrested when the component bears against a surface (104, 106). Thereafter a plurality of driving electrical pulses are applied to the motor (110) in dependence on the determination and when movement of the component is arrested to thereby drive the motor so as to cause the component to bear against the surface with greater force.