Band Brake Assembly for Robotic Joint Backdrivability Control
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Solution Overview
Problem
Robotic systems using DC motors face challenges with backdrivability, as they often run at higher speeds and lower torque, requiring transmission systems like gearboxes, which are bulky and introduce design and cost constraints, making it difficult to hold positions under weight and gravity when powered off.
Innovation Solution
A brake assembly system that includes a frame with a clearance area for the motor rotor, a brake band secured around the rotor, and a brake actuator with a permanent magnet and electromagnet, allowing for electronic control of the brake band to prevent motor rotation when powered off, reducing the need for gearboxes and enhancing backdrivability control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If DC motors are used for robotic systems, then speed is improved, but torque is reduced
Solution Approach 1:
The patent replaces the traditional mechanical gearbox transmission system with a magnetic braking system. The brake actuator uses electromagnetic fields (permanent magnet and electromagnet) to control the brake band, substituting mechanical gear reduction with magnetic field-based torque control and position holding.
Solution Approach 2:
The brake actuator changes the magnetic field parameters by energizing or de-energizing the electromagnet. When energized, the electromagnet attracts the brake band to apply braking force; when de-energized, the brake band releases. This parameter change allows dynamic control of torque and position without mechanical transmission components.
2Force
If gearboxes are used to increase torque, then torque is improved, but device complexity and size increase
Solution Approach 1:
The patent extracts and removes the gearbox transmission system from the robotic mechanism. By eliminating the mechanical gear train, the design reduces device complexity and size while maintaining torque control capabilities through the magnetic brake actuator system.
Solution Approach 2:
The mechanical gearbox is replaced with an electromagnetic brake actuator that uses magnetic fields to control torque and position. This substitution eliminates complex mechanical transmission components while achieving the desired torque control function.
3Stability of the object's composition
If gearboxes are used to hold position under weight and gravity, then position stability is improved, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical gearbox's position holding function with an electromagnetic brake system. The brake actuator uses magnetic fields to maintain position stability under gravity and weight loads, eliminating the need for complex mechanical transmission components.
Solution Approach 2:
The brake actuator provides self-service position holding by using the electromagnetic field to automatically maintain the brake band's position on the rotor. When energized, it maintains continuous contact to hold position; when de-energized, it releases automatically, providing adaptive position control without additional mechanical components.
4Ease of operation
If brake actuator with electromagnet is used to control brake band, then ease of operation is improved, but use of energy increases
Solution Approach 1:
The brake actuator uses periodic or intermittent energization of the electromagnet rather than continuous power consumption. The electromagnet is energized only when braking or position holding is required, and de-energized when not needed, reducing overall energy consumption while maintaining ease of operation through electronic control.
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
The brake assembly system effectively controls backdrivability, reduces system size and complexity, and facilitates new types of movements in robotic systems by allowing precise control over motor motion, even when powered off, thereby addressing the limitations of DC motors and gearboxes.
Implementation Method 1
a brake actuator with a permanent magnet and electromagnet, allowing for electronic control of the brake band to prevent motor rotation when powered off
Implementation Method 2
The brake assembly also includes a brake actuator including a permanent magnet at the distal end of the flexure arm and an electromagnet secured to the fame
Implementation Method 3
a brake band secured at one distal end along the clearance area, extending around a periphery of the clearance area, and secured at a second distal end at a flexure arm of the frame
Data Source
AI summary
A system and method for backdrivability control of end effectors in robotic systems are described. In one example, a robotic system includes a joint in a kinematic chain, an end effector at an end of the kinematic chain, and an assembly for backdrivability control of the joint. The assembly includes a frame comprising a flexure arm and a circular clearance area that extends around the joint, a brake band having one end secured along the circular clearance area and a second end secured at an end of the flexure arm, and a brake actuator configured to selectively pull the end of the flexure arm and tighten the brake band around the joint. The brake actuator can be actuated to tighten the brake band around the joint, arresting or dampening motion in the kinematic chain of the system for certain movements.