Robotic End-of-Arm Linkage for Direct Force Control
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Solution Overview
Problem
Existing end-of-arm tool assemblies for robotic manipulators rely on indirect force control schemes that require extra force sensors and are prone to instability due to contact modeling errors, lack safety in interaction, and are not backdrivable.
Innovation Solution
A direct force control scheme is implemented using a linkage assembly with low friction transmission between an actuator and finger assemblies, allowing precise force control without external measurement, and enabling mechanical backdrivability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If indirect force control schemes are used with position control or force plus position control, then the control system can operate with standard position control mechanisms, but the system requires extra force sensors at contact areas and is prone to instability due to contact modelling errors
Solution Approach 1:
The linkage assembly serves itself to provide force feedback through its mechanical structure. The low-friction transmission mechanism inherently reflects the relationship between actuator force and finger force without requiring external sensors, making the system self-measuring and eliminating the need for separate force sensing components
Solution Approach 2:
The patent replaces electronic force sensing and control systems with a mechanical transmission system. The linkage assembly's low-friction mechanical connection directly translates actuator force to finger force, substituting complex electronic force control with simple mechanical force transmission that is inherently stable and sensorless
2Ease of operation
If indirect force control through position is used, then the control can be implemented with position control schemes, but the control is prone to instability and poor control performance
Solution Approach 1:
The patent replaces position-based indirect force control with direct force control through a low-friction mechanical linkage. The transmission mechanism directly couples actuator force to finger force, eliminating the need for position-to-force transformation and associated modeling errors, thereby improving control performance while maintaining ease of implementation
Solution Approach 2:
The linkage assembly acts as an intermediary mechanical element that directly transmits force from the actuator to the finger assemblies. This mechanical mediator provides a direct force control pathway that bypasses the indirect position control route, eliminating instability caused by contact modeling while keeping the control system simple
3Force
If traditional actuator and transmission mechanisms are used, then the tool assembly can provide sufficient force, but the assembly is not backdrivable and less safe to interact with
Solution Approach 1:
The patent changes the friction parameter of the transmission system by using a low-friction linkage assembly. This parameter change enables backdrivability while maintaining sufficient gripping force, as the low friction allows manual override when needed but still transmits actuator force effectively during normal operation
Solution Approach 2:
The linkage assembly provides dynamic characteristics that allow the system to switch between actuated mode (sufficient gripping force) and manual backdrive mode (safe interaction). The low-friction mechanical connection enables the system to be driven in either direction depending on the operational requirement, providing adaptability between force generation and safe manual operation
4Power
If intermediate transmission devices such as gearing arrangements are used between actuator and linkage assembly, then the system can provide mechanical advantage, but backlash is introduced leading to errors in applied force
Solution Approach 1:
The patent extracts and removes the intermediate gearing arrangement from the transmission system. By eliminating the gear train, the design achieves direct force transmission from actuator to linkage assembly, removing the source of backlash while maintaining mechanical advantage through the direct mechanical connection and leverage principles
Solution Approach 2:
The patent merges the actuator and linkage assembly into a directly connected system without intermediate transmission elements. This consolidation eliminates the interface between separate components where backlash would occur, creating a unified force transmission path that maintains precision while preserving mechanical advantage through direct mechanical coupling
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 provides precise direct force control and mechanical backdrivability, ensuring safe interaction and minimizing backlash, making it suitable for handling items with varying characteristics.
Implementation Method 1
the linkage assembly is a low friction transmission device or arrangement, which, in this instance, is used to convert output force of the actuator to axially reciprocating movement of the finger assemblies
Data Source
AI summary
An end-of-arm tool assembly (16) for a robotic arm, the tool assembly comprising a housing (102) and an actuator (102) comprising two counter-moving components (104). The actuator is mounted within the housing such that both counter-moving components are movable. The tool assembly further comprises a linkage assembly (114) comprising two linkage subassemblies (116a, 116b). Each linkage sub-assembly connects the actuator to a finger assembly (120, 122). The actuator and link-age assembly are configured such that one of the linkage subassemblies is driven by one of the counter-moving components and the other of the linkage subassemblies is driven by the other of the counter-moving components.