Limb Assist Actuator Trunk Mounting Inertial Moment
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Solution Overview
Problem
Walk-assisting devices that restrict the entire lower limb result in significant inertial moments, making synchronous control difficult, leading to delayed responses, increased power consumption, discomfort, and fatigue for users.
Innovation Solution
A limb-assisting apparatus with a knee joint actuator positioned at the trunk, reducing inertial moment by detecting foot phases to provide assistive force only when necessary, and using a load detector to adjust the actuator's output, ensuring the actuator's weight is distributed to minimize load on the user's joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If support members tightly restrict the whole lower limb to provide assist force, then the assist force is sufficient, but the inertial moment becomes great and synchronous control becomes difficult
Solution Approach 1:
The lower limb support structure is divided into separate segments: upper leg support member and lower leg support member, which are independently controllable. This segmentation allows each segment to be controlled separately, reducing the overall inertial moment and simplifying synchronous control while still providing sufficient assist force through coordinated operation of the segments
Solution Approach 2:
The support members are designed with dynamic adjustment capabilities, allowing the system to adapt the level of restriction and assist force in real-time based on user needs. This dynamic control enables the system to provide sufficient assist force when needed while reducing restriction during phases where full support is not required, thereby reducing inertial moment and simplifying control
2Object-affected harmful factors
If an actuator with sufficient capacity is used to cancel the adverse effect of great inertial moment, then the inertial moment is compensated, but the joint driving unit becomes large-sized and consumes great power
Solution Approach 1:
The actuation system is segmented into separate actuators for the upper leg and lower leg, with the knee joint actuator positioned at the trunk. This segmentation allows each actuator to be smaller and consume less power individually, while collectively compensating for the inertial moment through coordinated operation
Solution Approach 2:
The drive unit acts as an intermediary mechanism that transfers the assist force from the knee joint actuator to the lower leg support member. This intermediary arrangement allows the actuator to be positioned at the trunk where space is available, reducing the need for large actuators at the limb joints and thereby reducing power consumption
3Force
If the whole lower limb is tightly restricted by support members, then the assist force is provided, but the user experiences uncomfortably restrictive feeling, pain and high load
Solution Approach 1:
The support members are divided into separate segments for upper and lower legs, allowing independent adjustment of restriction levels. This enables the system to provide necessary assist force in specific segments while leaving other segments more free, thereby improving user comfort and reducing the restrictive feeling and pain
Solution Approach 2:
The system dynamically adjusts the restriction parameters of the support members based on real-time detection of foot phase and user needs. During phases where full support is not required, the restriction is reduced to improve comfort; during phases requiring assist force, the restriction is increased to provide necessary support
4Force
If support members restrict the whole lower limb, then the assist force is provided, but the support members must be custom-built to be compatible with user figure and walking habit
Solution Approach 1:
The support members are designed with universal adjustment mechanisms that can accommodate different user figures and walking habits through parameter adjustment rather than custom manufacturing. The segmented design with independent control capabilities allows a single standardized design to serve multiple users with varying requirements
Data Source
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AI summary
An apparatus (1) for limb assisting includes a body attachment (10), a link for an upper leg (22), and a knee joint unit (23), a link for a lower leg (24), a lower limb attachment (30), a drive unit (50) and a knee joint actuator (42). The body attachment (10) is attached to a trunk of a user. The link for an upper leg (22) is placed alongside an upper leg of the user and coupled with the body attachment (10). The link for a lower leg (24) is placed alongside a lower leg of the user and coupled with the link for the upper leg (22) via the knee joint unit (23). The lower limb attachment (30) is attached to one of the lower leg and a foot of the user, and coupled with the link for a lower leg (24). The knee joint actuator (42) is placed in the body attachment (10) so as to apply rotational torque to the knee joint unit (23) via the drive unit (50).