Compact Exoskeleton Upper Limb With Rod-Driven Wrist Actuation
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Solution Overview
Problem
Existing exoskeleton upper limbs suffer from high inertia, complex kinematics, and bulky designs due to integrated geared motors, leading to low payloads, large footprints, and increased manufacturing costs, which adversely affect user comfort and application possibilities.
Innovation Solution
The exoskeleton upper limb features a frame with a front and rear support connected by a lattice structure, allowing for pronosupination rotation, and a handle actuated by separate kinematic chains with connecting rods and anti-rotation devices, reducing inertia and complexity through independent actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If integrated geared motors are used to actuate wrist rotations, then the actuation function is achieved, but the inertia and device complexity increase significantly
Solution Approach 1:
The patent divides the actuation system into separate kinematic chains for each degree of freedom (flexion/extension and adduction/abduction). Each chain has its own actuator mounted on the forearm segment, eliminating the need for integrated geared motors and reducing kinematic complexity while maintaining actuation reliability.
Solution Approach 2:
The patent introduces intermediate transmission elements (connecting rods, cranks, and transmission linkages) that mediate between the actuators and the handle. These intermediaries enable independent actuation of each wrist rotation without requiring complex integrated motor systems.
2Ease of operation
If one geared motor is integral with a support rotated by another geared motor, then the actuation function is achieved, but the weight and footprint increase
Solution Approach 1:
The patent segments the actuation system so that each actuator is independently mounted on the forearm segment and acts through its own kinematic chain. This eliminates the need for one motor to be integral with a support rotated by another motor, significantly reducing the weight and footprint of the forearm segment while maintaining ease of operation.
3Force
If the lever arm of the actuators produces great bending moment, then the actuation force is sufficient, but the local stresses and friction increase
Solution Approach 1:
The patent introduces transmission linkages with multiple rods and joints as intermediaries between the actuators and the handle. These intermediaries distribute the bending moments and reduce local stresses on the frame structure and rotational guidance, while still transmitting sufficient actuation force to move the handle.
Solution Approach 2:
The patent uses spatial transmission linkages that operate in multiple dimensions to transmit actuation force. This multi-dimensional transmission path reduces the bending moments on any single structural element, thereby reducing local stresses and friction in the rotational guidance.
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 design results in a more compact, reliable, and cost-effective exoskeleton with reduced actuator inertia, improved user comfort, and simplified control, enhancing application flexibility and reducing energy consumption.
Implementation Method 1
the first actuator comprises a first screw/nut assembly comprising a first nut cooperating with a first screw extending in a first direction substantially parallel to the longitudinal axis, a first anti-rotation device for blocking a rotation of the first nut relative to the first screw, a first motor designed to rotate the first screw about the first direction and cause linear movement of the first nut
Data Source
AI summary
An exoskeleton upper limb includes a frame and a connection interface movably mounted relative to the frame to perform a second rotation and a third rotation. The second rotation is actuated by a first kinematic chain of actuation including a first actuator. The third rotation is actuated by a second kinematic chain of actuation including a second actuator. The first kinematic chain includes a first connecting rod and/or the second kinematic chain includes a second connecting rod.