Tactile-Based Whole-Body Compliance With Force Propagation for Mobile Manipulators

Abstract

In this article, we propose a control method, providing mobile robots with whole-body compliance capabilities, in response to multi-contact physical interactions with their environment. The external forces applied to the robot, as well as their localization on its kinematic tree, are measured using a multimodal, self-configuring and self-calibrating artificial skin. We formulate a compliance control law in Cartesian space, as a set of quadratic optimization problems, solved in parallel for each limb involved in the interaction process. This specific formulation makes it possible to determine the torque commands required to generate the desired reactive behaviors, while taking the robot kinematic and dynamic constraints into account. When a given limb fails to produce the desired compliant behavior, the generalized force residual at the considered contact points is propagated to a parent limb in order to be adequately compensated. Hence, the robot's compliance range can be extended in a both robust and easily adjustable manner. The experiments performed on a dual-arm velocity-controlled mobile manipulator, show that our methodology is robust to nullspace interactions and robot physical constraints.

A Comprehensive Realization of Robot Skin: Sensors, Sensing, Control, and Applications

“…The objectives of this project were to set up a factory within 24 h, where the robot skin played an essential role. Later, using the same robot, we implemented a safe force propagation approach [70]. Then, we implemented a reactive grasp control in a 16-DOF robot hand.…”

“…In this section, we briefly present a control strategy that exploits the force and proximity feedback of our artificial skin to enhance the compliance range of a dual-arm mobile robot. This approach was presented in [70]. Operating in a human environment, robots must deal with a wide variety of physical interactions, likely to simultaneously occur at an arbitrary number of contact points.…”

“…In most approaches, active compliance is indeed implemented at the end-effector level [79] or at the joint level [80], resulting into potentially stiff configurations when interaction forces cannot be suitably detected or when singular configurations arise. It appears that formulating the compliance control at the contact point level allows to intuitively and precisely adjust the robot reactive behaviors at any point of its kinematic chain while providing information on null-space interactions [70], [77], [81]- [83]. In practice, covering a rigid robot with artificial skin provides it with a better awareness of its close contact environment, thereby greatly simplifying the structure of the underlying compliance control loop.…”

“…In practice, covering a rigid robot with artificial skin provides it with a better awareness of its close contact environment, thereby greatly simplifying the structure of the underlying compliance control loop. In [70], the proposed controller tracks a desired-potentially safe-reactive dynamics 0ẍ…”

A Separated Adaptive Control Strategy for Different Conditions Based on Flexible Dynamics Equation of Robot Manipulator

“…The robot, coupled by a mechanical system and a control system, exhibits a high nonlinearity [1]. During operation, the maximum acceleration of the robot is up to 3-5g, calling for a high precision in trajectory tracking [2]. For robot with a flexible structure, the excessive deformation of the manipulator, if not considered in the mathematical model, will have a great impact on the dynamic performance [3].…”