Motor Direction Control With Back-EMF Dynamic Braking
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Solution Overview
Problem
Existing actuation systems using frictional or positive locking brakes face issues with wear, reliability, and complexity, leading to inaccurate positioning and increased maintenance needs, especially in applications requiring precise actuator control.
Innovation Solution
Implement a system with a permanent magnet brushed direct current motor that uses dynamic braking by switching the motor's current direction to stop the motor before applying a positive locking brake, utilizing limit switches and a simplified actuation assembly to manage direction control and braking without complex H-bridge circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a frictional brake is used to hold the actuator output in position, then the brake can provide holding force, but the brake is subject to wear which affects stop position accuracy and requires periodic maintenance
Solution Approach 1:
The motor is dynamically braked before the frictional brake is applied, stopping the motor rotation in advance to prevent wear during the braking process. This preliminary stopping action ensures that the frictional brake only needs to hold the position without experiencing wear from active braking, thereby maintaining stop position accuracy and reducing maintenance needs
2Measurement precision
If a positive locking brake is used to achieve required position accuracy, then the position accuracy is improved, but the motor must stop before the brake is applied which requires a complex electronic controller with full H-bridge or half H-bridge
Solution Approach 1:
The complex H-bridge circuitry is removed from the system. Instead of using electronic switches and transistors to control motor direction and braking, the patent uses the motor's own back-EMF and a simple control assembly with limit switches to achieve dynamic braking and direction control, significantly reducing controller complexity while maintaining position accuracy
Solution Approach 2:
The motor's back-EMF is utilized to provide dynamic braking without requiring external power or complex control circuitry. The system uses the motor's own electrical characteristics to accomplish braking and direction control, eliminating the need for sophisticated H-bridge controllers
3Ease of operation
If a full H-bridge or half H-bridge is used for motor operation including directional control, then the motor can be precisely controlled, but additional EMI protection and specialized components for wide temperature range are required
Solution Approach 1:
The patent replaces complex electronic control systems with a simpler electromechanical approach using limit switches and the motor's inherent electrical characteristics. This substitution eliminates susceptibility to EMI and eliminates the need for specialized components required for wide temperature range operation
4Ease of operation
If complex circuitry with full H-bridge or half H-bridge is used for motor control, then directional control is achieved, but the system has increased failure rate and low reliability
Solution Approach 1:
The complex H-bridge circuitry with multiple transistors, switches, and control electronics is completely removed from the system. Directional control and dynamic braking are achieved using the motor's back-EMF and simple limit switches, dramatically reducing the number of potential failure points and improving overall system reliability
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 enhances reliability and reduces maintenance by eliminating the need for additional EMI protection and specialized components, while ensuring precise actuator positioning and effective braking across wide temperature ranges.
Implementation Method 1
stopping providing power to the motor forms a current loop for current from a counter electromotive force to flow through the motor and the brake for dynamic braking
Data Source
AI summary
Systems and methods for direction control of a motor and dynamic braking are disclosed. Systems and methods can use limit switches to not only switch the direction of motor current to provide directional control, but also to provide a path for current to flow for dynamic braking. Such current flow is produced by the motor's back electromotive force, and causes a torque to be developed which opposes motion. The torque can slow or stop a motor prior to applying a brake, limiting wear to the brake or allowing use of a positive locking brake. The limit switches and other components can be arranged to function symmetrically given different directions of current flow to allow for use of the systems and methods in forward and reverse actuation.