Legged Robot Normal Pendulum Body for Low-Torque Load Handling
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Solution Overview
Problem
Existing mobile robots with inverted pendulum bodies face challenges in balancing and energy efficiency, particularly when lifting heavy payloads, as they require significant holding torques and additional actuators for counterbalance.
Innovation Solution
The mobile robot employs a normal pendulum body (NPB) with the leg pivot above the center of mass (CoM) of the NPB, allowing for natural stable equilibrium and reducing the need for continuous balancing corrections. This design minimizes energy consumption by distributing payload weight effectively and eliminating the need for additional counterbalance actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an inverted pendulum body is used with the center of mass above the leg pivot, then the robot can achieve a humanoid structure and manipulate objects, but significant holding torques are required at the leg joints to maintain balance, especially when lifting heavy payloads
Solution Approach 1:
The patent inverts the traditional inverted pendulum configuration by placing the center of mass below the leg pivot point, creating a stable pendulum body. This inversion eliminates the need for continuous balancing corrections and significant holding torques, as the pendulum naturally returns to its equilibrium position. The manipulator is then connected to the pendulum body in a manner that allows it to move relative to the body, generating reaction torques that further balance the system without requiring excessive leg joint torques.
2Stability of the object's composition
If movable counterweights are used to align the center of mass with the required point, then balance can be maintained during motion, but additional actuators are required to drive the counterweight, increasing energy consumption
Solution Approach 1:
The stable pendulum body automatically self-balances through its inherent gravitational stability, eliminating the need for active actuators to move counterweights. The pendulum naturally returns to its equilibrium position with the center of mass below the pivot, providing passive balance maintenance during robot motion without requiring additional energy-consuming actuators.
3Loss of energy
If friction brakes are used to implement holding torques, then power consumption is reduced, but large incremental torques are required when the brakes are disengaged to adjust joint position
Solution Approach 1:
By inverting the pendulum configuration to create a stable body with the center of mass below the pivot, the system eliminates the need for high holding torques that would require friction brakes. The stable pendulum naturally maintains its position with minimal torque, and position adjustments require only small incremental torques to overcome static friction, rather than large torques needed in inverted configurations.
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 NPB design enhances energy efficiency and stability, enabling the robot to carry heavier payloads with reduced energy expenditure at the leg joints, compared to robots with inverted pendulum bodies or those using additional counterbalance actuators.
Implementation Method 1
the robot consists of at least one leg with one end of the leg connected to either foot or drive wheel and the other end connected to a normal pendulum body (NPB). Since the leg pivot to the NPB lies above the Center of Mass (CoM) of the NPB and if NPB were to be suspended on this pivot axis, it will assume a natural stable position with its CoM below that pivot axis.
Data Source
AI summary
A mobile robot includes a non-inverted pendulum body hereafter referred to as NPB with at least one pivot axis and this pivot axis divides the NPB into two portions. One portion of the NPB contains the center of mass of the NPB that can have structures to carry external payloads. The second portion of the NPB can have one or more manipulator arm and vision units. On the pivot axis is disposed at least one leg rotatabily coupled to the NPB. The other end of the leg has a foot joint on which is disposed a drive wheel or a foot. With additional degrees of freedom for each leg the robot can move similar to humanoids, be able to carry and sustain heavy loads with minimal leg joint torques and/or manipulate heavy loads and forces with self-compensating mass of the NPB while using minimal leg joint torques.