Differential Pulley Robot Actuator for Low Backlash Torque Control
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Solution Overview
Problem
Existing electric motor actuators for robotic and automation systems require efficient transmission systems that are lightweight, cost-effective, and capable of high torque and low speed operation, but current solutions like harmonic drives and cable drives are inefficient, expensive, and complex, with challenges in integrating torque sensors.
Innovation Solution
A differential pulley actuator system that uses input drive gears to couple motor rotation to an output pulley through timing belt pulleys, with idler pulleys suspended in tension, allowing for efficient gear reduction and low-backlash motion transmission, and enabling integration of torque sensors for closed-loop control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multi-stage gearboxes or harmonic drives are used for high torque and low speed operation, then gear ratio and load capacity are improved, but weight, cost, and complexity increase
Solution Approach 1:
The transmission system is divided into multiple independent timing belt stages, each providing a portion of the total gear reduction. This segmentation allows the use of lightweight timing belts instead of a single heavy multi-stage gearbox, distributing the torque multiplication across several lighter components.
Solution Approach 2:
Traditional heavy mechanical gearboxes and harmonic drives are replaced with a timing belt-based transmission system. The timing belts provide the necessary gear reduction through pulley ratios while being significantly lighter and simpler in construction than conventional mechanical transmissions.
2Power
If multi-stage gearboxes or harmonic drives are used for high torque and low speed operation, then gear ratio and load capacity are improved, but manufacturing cost increases
Solution Approach 1:
The transmission is segmented into multiple timing belt stages that can be manufactured using standard, cost-effective processes. Each stage uses off-the-shelf timing belts and pulleys, avoiding the expensive precision manufacturing required for harmonic drives and multi-stage gearboxes.
Solution Approach 2:
Standard timing belts and pulleys are used instead of expensive proprietary components. These components are commercially available, easily replaceable, and significantly cheaper to manufacture than harmonic drives or precision gearboxes, making the actuator cost-effective for consumer applications.
3Weight of moving object
If cable drive systems are used for lightweight and efficient operation, then weight and efficiency are improved, but transmission ratio complexity and cable management difficulty increase
Solution Approach 1:
Timing belts, which are flexible yet structurally robust, are used instead of traditional cable drives. These belts provide the necessary flexibility for compact routing while maintaining tension and preventing the cable management issues associated with wire-based torque sensors.
Solution Approach 2:
The timing belt serves multiple functions: it provides the primary torque transmission, acts as a structural element for mounting, and eliminates the need for separate cable management systems required by traditional cable drive approaches with torque sensors.
4Reliability
If torque sensors are integrated into cable drive transmissions, then closed loop torque control is achieved, but cable management complexity and manufacturing difficulty increase
Solution Approach 1:
The timing belt structure provides a rigid yet flexible mounting platform for torque sensors, eliminating the need for complex cable management that plagues cable drive systems. Sensors can be directly mounted on the timing belt or associated components, simplifying integration.
Solution Approach 2:
The timing belt acts as an intermediary structure that facilitates straightforward sensor mounting. Instead of attaching sensors to rotating cables or complex transmission components, the belt provides a stable, accessible surface for sensor integration, reducing manufacturing complexity.
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 differential pulley actuator achieves a wide range of gear ratios with low backlash and high load capacity, is lightweight and cost-effective, and allows for efficient integration of torque sensors, addressing the inefficiencies and complexity of existing systems.
Implementation Method 1
timing belt pulleys coupled together through the one or more input drive gears, and rotation of the one or more input drive gears causes rotation of a first timing belt pulley in a first direction
Data Source
AI summary
An example robot actuator utilizing a differential pulley transmission is provided. As an example, a differential pulley actuator includes input drive gears for coupling to a motor and timing pulleys coupled together through the input drive gears. Rotation of the input drive gears causes rotation of a first timing pulley in a first direction and rotation of a second timing pulley in a second direction opposite the first direction. The actuator also includes multiple idler pulleys suspended between the timing pulleys and the output pulley, and the multiple idler pulleys are held in tension between the timing pulleys via a first tension-bearing element and the output pulley via a second tension-bearing element. The first tension-bearing element loops around the timing pulleys and the multiple idler pulleys. The output pulley couple to a load, and is configured to apply motion of the multiple idler pulleys to the load.