Torque-Free Robot Arm Gravity Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing service robot arms are costly due to high prices and complex gravity compensation mechanisms that are difficult to apply to multi-degree-of-freedom mechanisms, limiting their application in service robots.
Innovation Solution
A torque-free robot arm equipped with a multi-degree-of-freedom counterbalance mechanism using pure mechanical elements like springs to compensate for gravitational torques at all joints, minimizing the need for motors and speed reducers, and incorporating a double parallelogram unit for efficient gravity compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gravity compensation mechanism is mounted at the shoulder part to counterbalance gravitational torques, then the robot arm can compensate for gravitational forces, but a considerable mounting space is needed and smooth compensation of high resolution is not easy due to a considerable range of compensation force for rotation angle
Solution Approach 1:
A parallelogram mechanism is introduced as an intermediary component to transmit and transform the compensation force from the shoulder joint to the elbow joint. This mechanism uses interconnected links and joints to maintain geometric relationships, allowing the compensation force to be distributed effectively across multiple joints while requiring minimal mounting space at the shoulder.
Solution Approach 2:
The compensation mechanism is extended from a single-joint (shoulder) approach to a multi-joint system by adding the parallelogram mechanism that connects shoulder and elbow joints. This dimensional extension allows the system to compensate for gravitational torques at multiple joints simultaneously, improving resolution and accuracy without proportionally increasing mounting space.
2Force
If existing gravity compensation mechanisms are designed for industrial robots, then they can provide sufficient counterbalancing force, but their size and counterbalancing method are difficult to apply to service robot arms
Solution Approach 1:
The compensation mechanism is designed with local optimization for service robots by positioning springs and counterbalancing elements directly at each joint (shoulder, elbow, wrist) rather than concentrating all compensation force at the shoulder. This distributed approach reduces the size requirements at each location while maintaining sufficient counterbalancing force locally at each joint.
Solution Approach 2:
The gravity compensation system is segmented into multiple independent counterbalancing units, each responsible for a specific joint. Each unit contains its own spring and mechanical elements tailored to the specific gravitational torque requirements of that joint, allowing the system to be adapted to different service robot configurations while maintaining effectiveness.
3Productivity
If motors and speed reducers are used to ensure work performance (payload, driving speed, work space), then the robot arm achieves required performance, but the cost spent reaches up to 90% of production costs
Solution Approach 1:
Springs and counterbalancing mechanisms are installed at each joint to generate forces that counteract the gravitational torque of the robot arm links. This passive mechanical counterbalancing reduces the net torque that motors must provide, allowing for the use of smaller, less expensive motors and speed reducers while maintaining the same payload capacity and work performance.
Solution Approach 2:
The counterbalancing mechanism uses the robot arm's own weight and geometry to generate compensating forces through springs and mechanical linkages. The system essentially serves itself by using its structural elements to create the counterbalancing forces needed, reducing reliance on expensive active motor control systems.
4Ease of manufacture
If a multi-degree-of-freedom counterbalance mechanism is developed to compensate for gravitational torques at all joints, then the required torques become zero and cost is reduced, but the mechanism complexity increases
Solution Approach 1:
The parallelogram mechanism serves multiple functions simultaneously: it transmits compensation force from the shoulder joint, maintains geometric relationships between joints, and provides structural support. This multi-functionality reduces the need for separate components for each function, thereby reducing overall system complexity despite the multi-degree-of-freedom requirement.
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 solution reduces manufacturing costs, enables accurate and rapid motion, and achieves stable gravity compensation, making it suitable for compact service robot designs while minimizing the load on robot mass.
Implementation Method 1
a first compression spring disposed between the first spring block and the first pressing flange
Implementation Method 2
compensates for gravitational torques generated by the robot mass
Data Source
AI summary
The present invention provides a torque-free robot arm, comprising: a base unit; and a first link in which one end is rotatably connected to the base unit to form a first joint as a rotary shaft horizontal to the ground and the center of gravity is separated from the first joint, wherein the first link includes one end arranged at the first joint, the other end arranged along the longitudinal direction of the first link, and a first counter balancer for compensating the gravity of the first link when the first link is rotated around the first joint.