Exoskeleton Actuator Design for Weight Reduction
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Solution Overview
Problem
Existing orthopaedic exoskeletons for rehabilitating motion-injured individuals, such as those with paraplegia, are cumbersome and unsuitable for supporting the entire patient weight, requiring patients to lean on fixed bars during exercises due to the placement of actuators and their attachment points, which limits their usability and comfort.
Innovation Solution
The exoskeleton design is enhanced by minimizing the number of actuators, using electrically driven mechanical cylinders with epicycloidal reducers and recirculating ball screws for linear actuation, and positioning actuators to reduce weight and encumbrance, allowing for easier use in narrow spaces and noiseless operation, with an electronic control unit and remote control for seamless transitions between upright and seated positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional actuators (hydraulic or compressed air cylinders) are used in the exoskeleton, then the exoskeleton can move the lower jointed parts, but the apparatus becomes too heavy and cannot hold the entire patient weight, requiring patients to lean on fixed bars
Solution Approach 1:
The patent replaces traditional hydraulic or compressed air actuators with electric motors that drive screw mechanisms. This substitution reduces the overall weight of the actuation system while maintaining the force output needed to support patient weight during rehabilitation exercises.
Solution Approach 2:
The patent changes the actuation mechanism from direct-acting hydraulic/pneumatic cylinders to electric motors with mechanical advantage systems (screws). This parameter change in the actuation system allows for reduced weight while preserving the necessary force generation capability to support the patient's body weight.
2Ease of operation
If actuators are positioned close to the hip and knee joints for effective leverage, then the exoskeleton can effectively move the limbs, but the apparatus becomes cumbersome and unsuitable for perambulating through corridors or doors of limited width
Solution Approach 1:
The patent extracts or removes the heavy hydraulic/pneumatic actuation systems from the exoskeleton structure and replaces them with compact electric motor-driven screw mechanisms. This extraction of the bulky actuation system reduces the overall encumbrance and width of the exoskeleton, making it suitable for perambulation through narrow corridors and doors while maintaining effective leverage at the joint positions.
3Power
If traditional compressed air or hydraulic actuators are used, then the exoskeleton can provide powered movement, but the operation of the apparatus becomes noisy
Solution Approach 1:
The patent substitutes noisy compressed air or hydraulic actuators with electric motors that drive screw mechanisms. This replacement eliminates the noise associated with compressed air release and hydraulic system operation, providing the necessary actuator power for limb movement while maintaining quiet operation during rehabilitation exercises.
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 reduces the exoskeleton's weight and encumbrance, facilitates easier donning, and enables quiet operation, enhancing patient mobility and comfort by allowing efficient and controlled movement between upright and seated positions without the need for patients to lean on fixed bars.
Implementation Method 1
an epicycloidal reducer
Implementation Method 2
a recirculating ball screw for a linear actuation of the cylinder pushing/pulling rod or tube
Implementation Method 3
an electric motor
Data Source
Figure 1~2
Figure 3~4
Figure 5A~5B
AI summary
Orthopaedic apparatus for Walking and rehabilitating a motion-injured person, with an exoskeleton to support the patient's body, comprising: - articulated rods (1, 2, 3) set along the patient's trunk, thighs and legs and connected by pins (4, 5) opposite the hip and knee joints, - a pair of plates (6) set externally along the knee joints, - a bodice (13) fitted to the patient's trunk connecting the exoskeleton's rods flanking the patients trunk, - first and second actuators (7, 8) hinged to said plates and said articulated rods flanked at the side of the patient's trunk and leg, respectively, capable of imparting motions on said rods corresponding to those of a human gait and to those for movig from a seated to an upright position and vice versa, said actuators being of a mechanical cylinder type, fitted internally with ean electric motor, an epicycloidal reducer, and a recirculating ball screw for a linear actuation of the cylinder pushing/pulling rod or tube, - an electronic control unit (24) with remote control, connected to said actuators to impart said motions to said articulated rods.