Quadruped Height Control Under Non-Constant Body Pitch
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Solution Overview
Problem
The complexity of robotic control is increased by varying body pitch and height fluctuations in quadruped robots, particularly during gaits like running or galloping, as traditional control systems struggle to account for non-constant body pitch, affecting height control and stability.
Innovation Solution
A model decouples height control between different pairs of legs, using a 'barbell' model to represent the robot as two separate point masses, allowing independent height controllers for each pair of legs, enabling independent control of vertical forces without affecting the other pair's height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional control systems are used for quadruped robots with varying body pitch, then the robot can perform basic locomotion, but the height control complexity increases and stability deteriorates
Solution Approach 1:
The control system is segmented into four independent height controllers, one for each leg, rather than a single centralized controller. Each controller independently manages the height of its associated leg, simplifying the control logic for each individual controller while collectively managing the complex task of maintaining stability during varying body pitch movements.
Solution Approach 2:
The system dynamically adjusts the body pitch angle as a explicit parameter during locomotion. By making the body pitch angle a dynamic variable that is explicitly tracked and compensated for in real-time, the system can maintain stable height control even during gaits like running or galloping where the body pitch naturally varies.
2Measurement precision
If independent height controllers are implemented for each leg, then height control precision improves, but the device complexity increases
Solution Approach 1:
The control system is divided into four independent height controllers, one for each leg, allowing each controller to precisely manage its associated leg's height independently. This segmentation enables high precision height control for each leg while keeping each individual controller's logic relatively simple and modular.
Solution Approach 2:
The system implements four independent height controllers (one per leg) rather than fewer controllers, which is more than traditionally used. This excessive action provides redundant control capability and precise height management for each leg, with the added benefit that not all controllers need to be active simultaneously, reducing the effective complexity at any given moment.
3Device complexity
If body pitch is kept constant during locomotion, then height control becomes simpler, but the robot's adaptability to different gaits deteriorates
Solution Approach 1:
The system dynamically adjusts the body pitch angle as a explicit parameter during locomotion. By making the body pitch angle a dynamic variable that is explicitly tracked and compensated for in real-time, the system can maintain stable height control even during gaits like running or galloping where the body pitch naturally varies.
Solution Approach 2:
The system changes the parameter representation by explicitly incorporating body pitch angle as a dynamic parameter in the height control calculations. This parameter change allows the controllers to compensate for pitch variations and maintain accurate height control across different gaits and locomotion modes.
Data Source
AI summary
An example implementation involves controlling robots with non-constant body pitch and height. The implementation involves obtaining a model of the robot that represents the robot as a first point mass rigidly coupled with a second point mass along a longitudinal axis. The implementation also involves determining a state of a first pair of legs, and determining a height of the first point mass based on the model and the state of the first pair of legs. The implementation further involves determining a first amount of vertical force for at least one leg of the first pair of legs to apply along a vertical axis against a surface while the at least one leg is in contact with the surface. Additionally, the implementation involves causing the at least one leg of the first pair of legs to begin applying the amount of vertical force against the surface.