Knee Joint Series Elastic Actuator Crank Mechanism
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Solution Overview
Problem
Conventional active method knee joints are costly and heavy due to their complex structure, with poor energy efficiency and durability issues, and existing solutions like series elastic actuators complicate the mechanism and increase size and weight when trying to widen the movable range.
Innovation Solution
A knee joint design incorporating a drive section with a series elastic mechanism and a crank mechanism, where the series elastic mechanism includes a driven member, an elastic member, and a linear motion member, and the crank mechanism converts linear motion to rotational motion, supported by a frame with a motor, speed change mechanism, and ball screw, allowing for efficient energy use and reduced size and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional active method knee joint uses a motor mounted on the knee joint to actively control bending angle, then knee joint movement for operations such as going up and down stairs is supported, but cost is high due to complicated structure and the knee joint becomes large and heavy due to poor energy efficiency requiring a large capacity battery
Solution Approach 1:
The patent replaces the conventional motor-driven mechanical system with a series elastic actuator system that converts hydraulic pressure into linear motion. This substitution eliminates the need for a heavy motor and battery while maintaining the active control capability for knee joint movement during various operations including going up and down stairs.
Solution Approach 2:
The patent introduces a hydraulic pressure cylinder that generates linear motion through hydraulic pressure. This hydraulic mechanism replaces the electric motor system, providing a more energy-efficient and lighter-weight solution while maintaining the ability to actively control knee joint bending angle for various movements.
2Use of energy by moving object
If a series elastic actuator is used to convert linear motion to rotational motion of the knee using a belt and pulleys, then walking energy is utilized with high energy efficiency, but the mechanism becomes extremely complicated with many components and the knee joint becomes large and heavy
Solution Approach 1:
The patent extracts and eliminates the complex belt and pulley transmission system from the series elastic actuator mechanism. By directly connecting the linear motion member to the knee joint rotation, it removes unnecessary intermediate components while preserving the high energy efficiency benefit of the series elastic actuator.
Solution Approach 2:
Instead of using a belt and pulleys to convert linear motion to rotational motion, the patent inverts the approach by directly utilizing the linear motion of the series elastic actuator to drive the rotation of the knee joint through a simplified mechanical linkage, thereby reducing component count and complexity.
3Adaptability or versatility
If the movable range of the knee joint is widened with a belt and pulley system, then the range of motion is increased, but the belt and pulley become large in size making the knee joint difficult to use
Solution Approach 1:
The patent removes the belt and pulley system that caused size increase when widening the movable range. By using a direct mechanical linkage between the linear motion member and knee joint, it achieves an extended range of motion without the need for large-sized transmission components.
4Device complexity
If a linear actuator is directly connected to the knee member without a reduction gear to supplement rotational movement, then the structure is simplified, but a high load acts on the linear actuator to acquire high driving torque
Solution Approach 1:
The patent changes the operational parameters of the linear actuator by utilizing the series elastic mechanism to provide mechanical advantage. This allows the linear actuator to operate at lower loads while still achieving the required high driving torque for knee joint rotation, maintaining structural simplicity without excessive force requirements.
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 design achieves good energy efficiency, reduces size and weight, and maintains a broad movable range while being cost-effective, with improved durability and reduced maintenance costs compared to traditional active method knee joints.
Implementation Method 1
the elastic member is arranged between the driven member and the linear motion member, the linear motion member is configured to elastically move in at least one direction, in accordance with movement of the driven member, by way of the elastic member
Implementation Method 2
the crank mechanism is configured to convert linear motion of the linear motion member to rotational motion
Data Source
AI summary
A knee joint that is capable of widening a moveable range, and that has good energy efficiency and is small and lightweight is described. Also described is a knee joint that is of an active type, but comparatively inexpensive. A drive section moves a driven member. An elastic member is arranged between the driven member and a linear motion member. The linear motion member elastically moves in at least one direction, in accordance with movement of the driven member, by way of the elastic member. A crank mechanism can realize bending and extension of the knee joint by converting linear motion of the linear motion member to rotational motion.