In this work, we present a highly functional teleoperation system, that integrates a full-body inertia-based motion capture suit and three intuitive teleoperation strategies with a Whole-Body Control (WBC) framework, for quadrupedal legged manipulators. This enables the realisation of commands from the teleoperator that would otherwise not be possible, as the framework is able to utilise DoF redundancy to meet several objectives simultaneously, such as locking the gripper frame in position while the trunk completes a task. This is achieved through the WBC framework featuring a defined optimisation problem that solves a range of Cartesian and joint space tasks, while subject to a set of constraints (e.g. halt constraints). These tasks and constraints are highly modular and can be configured dynamically, allowing the teleoperator to switch between teleoperation strategies seamlessly. The overall system has been tested and validated through a physics-based simulation and a hardware test, demonstrating all functionality of the system, which in turn has been used to evaluate its effectiveness.
The task of performing locomotion and manipulation simultaneously poses several scientific challenges, such as how to deal with the coupling effects between them and how to cope with unknown disturbances introduced by manipulation. This paper presents an inverse dynamics-based whole-body controller for a torque-controlled quadrupedal manipulator capable of performing locomotion while executing manipulation tasks. Unlike existing methods that deal with locomotion and manipulation separately, the proposed controller can handle them uniformly, which can take into account the coupling effects between the base, limbs and manipulated object. The controller tracks the desired task–space motion references based on a hierarchical optimization algorithm, given a set of hierarchies that define strict priorities and the importance of weighting each task within a hierarchy. The simulation results show the robot is able to follow multiple task–space motion reference trajectories with reasonable deviation, which proved the effectiveness of the proposed controller.
Legged locomotion poses significant challenges due to its nonlinear, underactuated and hybrid dynamic properties. These challenges are exacerbated by the high-speed motion and presence of aerial phases in dynamic legged locomotion, which highlights the requirement for online planning based on current states to cope with uncertainty and disturbances. This article proposes a real-time planning and control framework integrating motion planning and whole-body control. In the framework, the designed motion planner allows a wider body rotation range and fast reactive behaviors based on the 3-D single rigid body model. In addition, the combination of a Bézier curve based trajectory interpolator and a heuristic-based foothold planner helps generate continuous and smooth foot trajectories. The developed whole-body controller uses hierarchical quadratic optimization coupled with the full system dynamics, which ensures tasks are prioritized based on importance and joint commands are physically feasible. The performance of the framework is successfully validated in experiments with a torque-controlled quadrupedal robot for generating dynamic motions.
Legged manipulators are a prime candidate for reducing risk to human lives through completing tasks in hazardous environments. However, controlling these systems in real-world applications requires a highly functional teleoperation framework, capable of leveraging all utility of the robot to complete tasks. In this work, such a teleoperation framework is presented, where a wearable whole-body motion capture suit is integrated with a whole-body controller specialised for teleoperation and a set of teleoperation strategies that enable the control of all main frames of the robot along with additional functions. Within the whole-body controller, all tasks and constraints can be configured dynamically due to their modularity, hence enabling seamless transitions between each teleoperation strategy. As a result, this not only enables the realisation of trajectories outside the workspace without the whole-body controller but also the ability to complete tasks that would require an additional manipulator if just the gripper frames of the robot were controllable. To validate the presented framework, a set of real robot experiments have been completed to demonstrate all teleoperation strategies and analyse their proficiency.
With teleoperation currently being the optimal method of controlling legged robots in real world applications, there presents the demand for a teleoperation framework offering extensive functionality. As such, this paper presents a teleoperation framework that, with the implementation of a set of teleoperation strategies, enables a teleoperator to control the gripper, trunk and front left (FL) foot frames of a legged manipulator while utilising the robot's redundancy through the use of a Whole-body controller (WBC). This enables the teleoperator to utilise these frames to complete real world tasks, as demonstrated in this paper with the teleoperation framework being used to dispose an item in a push peddle bin.
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