Brushless DC Motor Haptic Feedback Without Force Sensors
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Solution Overview
Problem
Active tactile force feedback systems are costly due to the need for high-quality components like force sensors, precision gear-trains, and complex electronic systems, which increase the expense and complexity of implementing reliable haptic feedback.
Innovation Solution
The system employs brushless DC motors and vector control drive methods to generate haptic feedback without force sensors or a force control loop, using Hall sensors for discrete motor position information and built-in springs and dampers to provide tactile feedback, reducing the number of electronic components and eliminating the need for position resolvers and cog-less motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active tactile force feedback systems use high-quality components like force sensors, precision gear-trains, and complex electronic systems, then the haptic feedback quality is improved, but the system cost and complexity increase
Solution Approach 1:
The patent extracts and eliminates the force sensor from the traditional haptic feedback system. Instead of using a force sensor to measure operator input force, the system uses the brushless DC motor's own current measurement to determine the force applied by the operator, thereby simplifying the system while maintaining haptic feedback quality
Solution Approach 2:
The brushless DC motor serves multiple functions: it acts as both the actuator to move the controlled element and as the force sensor to detect operator input. The motor's current measurement provides force information, eliminating the need for a separate force sensing system and reducing overall system complexity
2Measurement precision
If active tactile force feedback systems use force sensors and precision components, then the haptic feedback accuracy is improved, but the system cost increases
Solution Approach 1:
The system uses the brushless DC motor's built-in current sensing capability to measure the force applied by the operator. The motor essentially measures its own operating conditions, eliminating the need for external force sensors and reducing system cost while maintaining measurement accuracy
Solution Approach 2:
The system changes the measurement parameter from direct force sensing to current measurement. By measuring the current drawn by the brushless DC motor, the system indirectly but accurately determines the force applied by the operator, providing a cost-effective alternative to expensive force sensors
3Device complexity
If the system uses Hall sensors for motor position information instead of position resolvers, then the system complexity is reduced, but the motor position resolution may be affected
Solution Approach 1:
The patent replaces the mechanical position resolver system with electronic Hall sensors. The Hall sensors provide sufficient position information for the haptic feedback application, simplifying the system while maintaining adequate position resolution through electronic rather than mechanical means
4Ease of manufacture
If the system eliminates force sensors and uses brushless DC motors with vector control, then the system cost is reduced, but the torque ripple increases
Solution Approach 1:
The system uses dynamic current control to compensate for torque ripple in the brushless DC motor. By continuously adjusting the motor currents based on position and force feedback, the system minimizes the harmful torque ripple effects while maintaining cost-effectiveness
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 reduces costs and complexity by eliminating the need for force sensors and position resolvers, while providing high-resolution motor position determination and minimizing torque ripple, enabling effective haptic feedback without the added expenses of sinusoidal or field control methods.
Implementation Method 1
a brushless DC motor configured to actuate a mechanical output based on a plurality of phase power signals
Implementation Method 2
using Hall sensors for discrete motor position information
Data Source
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AI summary
The subject matter of this specification can be embodied in, among other things, a motion control apparatus that includes a brushless DC motor to actuate a mechanical output based on a collection of phase power signals, a collection of first Hall effect sensors configured to provide a collection of first feedback signals in response to a sensed motor position and a sensed motor speed, a controller configured to determine a speed and position of the motor based on the feedback signals, and determine an electrical current level based on a collection of operational parameters and feedback signals including a position of the mechanical output, the motor speed, and the motor position, a current controller configured to provide electrical phase sequence output signals based on the electrical current level, and a motor driver configured to provide the collection of phase power signals based on the electrical phase sequence output signals.