ControlIt! — A Software Framework for Whole-Body Operational Space Control

Abstract

Whole Body Operational Space Control (WBOSC) is a pioneering algorithm in the field of human-centered Whole-Body Control (WBC). It enables floating-base highlyredundant robots to achieve unified motion/force control of one or more operational space objectives while adhering to physical constraints. Although there are extensive studies on the algorithms and theory behind WBOSC, limited studies exist on the software architecture and APIs that enable WBOSC to perform and be integrated into a larger system. In this paper we address this by presenting ControlIt!, a new opensource software framework for WBOSC. Unlike previous implementations, ControlIt! is multi-threaded to increase servo frequencies on standard PC hardware. A new parameter binding mechanism enables tight integration between ControlIt! and external processes via an extensible set of transport protocols. To support a new robot, only two plugins and a URDF model needs to be provided -the rest of ControlIt! remains unchanged. New WBC primitives can be added by writing a Task or Constraint plugin. ControlIt!'s capabilities are demonstrated on Dreamer, a 16-DOF torque controlled humanoid upper body robot containing both series elastic and co-actuated joints, and using it to perform a product disassembly task. Using this testbed, we show that ControlIt! can achieve average servo latencies of about 0.5ms when configured with two Cartesian position tasks, two orientation tasks, and a lower priority posture task. This is significantly higher than the 5ms that was achieved using UTA-WBC, the prototype implementation of WBOSC that is both application and platform-specific. Variations in the product's position is handled by updating the goal of the Cartesian position task. ControlIt!'s source code is released under an LGPL license and we hope it will be adopted and maintained by the WBC community for the long term as a platform for WBC development and integration.main ControlIt! -A Software Framework for Whole-Body Operational Space Control 3 (6) We demonstrate ControlIt!'s utility and performance using a humanoid robot executing a product disassembly task.The remainder of this paper is organized as follows. Section 2 discusses related work. Section 3 provides an overview of WBOSC's mathematical foundations. Section 4 presents ControlIt!'s software architecture and APIs. Section 5 presents how ControlIt! was integrated with Dreamer and used to develop a product disassembly task. Section 6 contains a discussion on other experiences using ControlIt! and future research directions. The paper ends with conclusions in Section 7. These efforts demonstrate the behaviors enabled by WBC such as the use of compliance, multi-contact postures, robot dynamics, and joint redundancy to balance multiple competing objectives. ControlIt! is currently focused on supporting general use of WBOSC and its capabilities, but may be enhanced to include ideas and capabilities from these recent WBC developments.An implementation of WBOSC called Stanford-WBC 68 was released in 2011. Stanford-...

Real-time whole-body motion generation using torso posture regression and center of mass

“…In the second category, Fok et al used a numerical method (i.e., Jacobian-based) to solve the IK of the whole body [14]. Their main concern was implementing a middleware structure, not accelerating the calculation.…”

Manipulation and Control

“…The system prototype of WBOSC was also extended to include the possibility of internal force control and is available as an open-source software named ControlIt! [121]. Figure 5.28 shows the overall control diagram proposed by WBOSC as well as the joint torque controllers.…”

A Unified Robust Motion Controller Design for Series Elastic Actuators

“…In order to improve the robustness, stability and performance of position control, robots are designed by using stiff and nonback-drivable mechanical components [4]. However, several studies have showed that accurate position control is not sufficient to perform fine motion tasks in which robots interact with environments, e.g., grinding and polishing [5][6][7]. Although explicit and implicit force control methods have been proposed to perform fine motion tasks by actively adjusting the compliance of stiff robots, they suffer from low performance, stability and safety problems in practice [8][9][10][11].…”

“…In the new era of robotics, physical interaction with unstructured and dynamic environments becomes a more dominant requirement for many advanced robot applications, e.g., rehabilitation, humanoids and human-robot collaboration [5][6][7]. Against traditional robotics "stiffer is better" rule of thumb, passive compliance control, in which robots have intrinsic compliant elements, has been proposed to overcome the fundamental performance, stability and safety problems of conventional stiff robots [14][15][16].…”