scholarly journals Whole-Body Operational Space Control for Locomotion and Manipulation

2015 ◽  
Vol 137 (06) ◽  
pp. S2-S6
Author(s):  
Luis Sentis
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Humanoid Robots ◽  
Rigid Body Dynamics ◽  
Joint Torque ◽  
Whole Body ◽  
Operational Space ◽  
Body Dynamics ◽  
Service Oriented ◽  
High Level

This article discusses the various researches being undertaken to study and develop Whole-Body Operational Space Control (WBOSC). The WBOSC emerges as a capable framework for real-time unified control of motion and force of humanoid robots. It could theoretically outperform high-speed industrial manipulators while providing the grounds for new types of service-oriented applications that require contact, by exploiting the rigid body dynamics of systems. By relying on joint torque sensors, WBOSC opens up the potential to interact with the physical environment using any part of the robot’s body while regulating the effective mechanical impedances to safe values. With ControlIt!, the developers provide a strict and easy way to use the WBOSC API consisting of compound tasks which define the operational space, and constraint sets that define the contacts with the environment as well as dependent degrees of freedom. ControlIt! is easy to connect to high level planners.

Optimization-Based Whole-Body Control of a Series Elastic Humanoid Robot

2016 ◽  
Vol 13 (01) ◽  
pp. 1550034 ◽  
Author(s):  
Michael A. Hopkins ◽  
Alexander Leonessa ◽  
Brian Y. Lattimer ◽  
Dennis W. Hong
Keyword(s):  
Inverse Dynamics ◽  
Contact Forces ◽  
Joint Torque ◽  
Whole Body ◽  
Quadratic Program ◽  
Successful Implementation ◽  
Control Approach ◽  
Floating Base ◽  
High Level ◽  
Series Elastic

As whole-body control approaches begin to enter the mainstream of humanoid robotics research, there is a real need to address the challenges and pitfalls encountered in hardware implementations. This paper presents an optimization-based whole-body control framework enabling compliant locomotion on THOR, a 34 degree of freedom humanoid featuring force-controllable series elastic actuators (SEAs). Given desired momentum rates of change, end-effector accelerations, and joint accelerations from a high-level locomotion controller, joint torque setpoints are computed using an efficient quadratic program (QP) formulation designed to solve the floating-base inverse dynamics (ID). Constraints on the centroidal dynamics, frictional contact forces, and joint position/torque limits ensure admissibility of the optimized joint setpoints. The control approach is supported by an electromechanical design that relies on custom linear SEAs and embedded joint controllers to accurately regulate the internal and external forces computed by the whole-body QP. Push recovery and walking tests conducted using the THOR humanoid validate the effectiveness of the proposed approach. In each case, balancing is achieved using a planning and control approach based on the time-varying divergent component of motion (DCM) implemented for the first time on hardware. We discuss practical considerations that led to the successful implementation of low-impedance whole-body control on our hardware system including the design of the robot’s high-level standing and stepping behaviors and low-level joint-space controllers. The paper concludes with an application of the presented approach for a humanoid firefighting demonstration onboard a decommissioned US Navy ship.

Whole-Body Balancing Walk Controller for Position Controlled Humanoid Robots

2016 ◽  
Vol 13 (01) ◽  
pp. 1650011 ◽  
Author(s):  
Seung-Joon Yi ◽  
Byoung-Tak Zhang ◽  
Dennis Hong ◽  
Daniel D. Lee
Keyword(s):  
Hierarchical Control ◽  
Humanoid Robots ◽  
Whole Body ◽  
Appropriate Behavior ◽  
Low Level ◽  
Push Recovery ◽  
Hierarchical Control Architecture ◽  
High Level ◽  
Experimental Trials ◽  
Decision Boundaries

Bipedal humanoid robots are intrinsically unstable against unforeseen perturbations. Conventional zero moment point (ZMP)-based locomotion algorithms can reject perturbations by incorporating sensory feedback, but they are less effective than the dynamic full body behaviors humans exhibit when pushed. Recently, a number of biomechanically motivated push recovery behaviors have been proposed that can handle larger perturbations. However, these methods are based upon simplified and transparent dynamics of the robot, which makes it suboptimal to implement on common humanoid robots with local position-based controllers. To address this issue, we propose a hierarchical control architecture. Three low-level push recovery controllers are implemented for position controlled humanoid robots that replicate human recovery behaviors. These low-level controllers are integrated with a ZMP-based walk controller that is capable of generating reactive step motions. The high-level controller constructs empirical decision boundaries to choose the appropriate behavior based upon trajectory information gathered during experimental trials. Our approach is evaluated in physically realistic simulations and on a commercially available small humanoid robot.

scholarly journals Coupling linear sloshing with six degrees of freedom rigid body dynamics

2015 ◽  
Vol 54 ◽  
pp. 17-26 ◽  
Author(s):  
François Dubois ◽  
Dimitri Stoliaroff ◽  
Isabelle Terrasse
Keyword(s):  
Rigid Body ◽  
Degrees Of Freedom ◽  
Rigid Body Dynamics ◽  
Six Degrees Of Freedom ◽  
Body Dynamics

Development of dynamic base model of a bogie suspended forwarder

2016 ◽  
Vol 231 (2) ◽  
pp. 357-371 ◽  
Author(s):  
Abbos Ismoilov ◽  
Ulf Sellgren ◽  
Kjell Andersson
Keyword(s):  
Simulation Model ◽  
Degrees Of Freedom ◽  
Dynamics Simulation ◽  
Whole Body ◽  
Rough Terrain ◽  
Tyre Model ◽  
Body Dynamics ◽  
Dynamic Simulation Model ◽  
Multi Body ◽  
Whole Body Vibrations

A forwarder is an off-road working machine that is used to transport logs from logging sites to a landing area that is accessible by trucks. Soil damage and operator comfort, especially whole-body vibrations when operating on hard and rough terrain, are crucial issues when developing novel forest machines. Most forwarders on the market are heavy machines with articulated steering and they are equipped with pairs of wheels mounted on bogies. For such bogie machines, only the flexibility and the dynamic dissipation in the tyres contribute to the “chassis damping”. The roll and lateral motions are the most severe components of the whole-body vibrations. So, developing new traction units, chassis suspensions and/or cabin suspension are in focus. Model-based design relies on focused models that are as simple as possible, but not too simple. This paper presents a 12 degrees-of-freedom multi-body dynamics simulation model of a standard eight-wheeled bogie type of medium-sized forwarder. The presented model is targeted for assessing and comparing different design solutions. It is shown that a configuration of seven rigid subsystems and eight flexible tyres represented with the simple and computer efficient Fiala tyre model enables the forwarder dynamic simulation model to be used to predict the roll and lateral motions of a forwarder operating on hard and rough terrain.

scholarly journals A Compact, Bone-Attached Robot for Mastoidectomy

2015 ◽  
Vol 9 (3) ◽  
Author(s):  
Neal P. Dillon ◽  
Ramya Balachandran ◽  
J. Michael Fitzpatrick ◽  
Michael A. Siebold ◽  
Robert F. Labadie ◽  
...  
Keyword(s):  
Computed Tomography ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Compact Bone ◽  
Target Volume ◽  
Surgical Workflow ◽  
The Mean ◽  
Milling Robot ◽  
High Level ◽  
Temporal Bones

Otologic surgery often involves a mastoidectomy, which is the removal of a portion of the mastoid region of the temporal bone, to safely access the middle and inner ear. The surgery is challenging because many critical structures are embedded within the bone, making them difficult to see and requiring a high level of accuracy with the surgical dissection instrument, a high-speed drill. We propose to automate the mastoidectomy portion of the surgery using a compact, bone-attached robot. The system described in this paper is a milling robot with four degrees-of-freedom (DOF) that is fixed to the patient during surgery using a rigid positioning frame screwed into the surface of the bone. The target volume to be removed is manually identified by the surgeon pre-operatively in a computed tomography (CT) scan and converted to a milling path for the robot. The surgeon attaches the robot to the patient in the operating room and monitors the procedure. Several design considerations are discussed in the paper as well as the proposed surgical workflow. The mean targeting error of the system in free space was measured to be 0.5 mm or less at vital structures. Four mastoidectomies were then performed in cadaveric temporal bones, and the error at the edges of the target volume was measured by registering a postoperative computed tomography (CT) to the pre-operative CT. The mean error along the border of the milled cavity was 0.38 mm, and all critical anatomical structures were preserved.

scholarly journals HUMANOID LOCOMOTION PLANNING FOR VISUALLY GUIDED TASKS

2012 ◽  
Vol 09 (02) ◽  
pp. 1250009 ◽  
Author(s):  
JEAN-BERNARD HAYET ◽  
CLAUDIA ESTEVES ◽  
GUSTAVO ARECHAVALETA ◽  
OLIVIER STASSE ◽  
EIICHI YOSHIDA
Keyword(s):  
Visual Servoing ◽  
Nonholonomic Constraints ◽  
Humanoid Robots ◽  
Body Motion ◽  
Whole Body ◽  
Visually Guided ◽  
Open Spaces ◽  
The Gaze ◽  
High Level ◽  
Path Planner

In this work, we propose a landmark-based navigation approach that integrates (1) high-level motion planning capabilities that take into account the landmarks position and visibility and (2) a stack of feasible visual servoing tasks based on footprints to follow. The path planner computes a collision-free path that considers sensory, geometric, and kinematic constraints that are specific to humanoid robots. Based on recent results in movement neuroscience that suggest that most humans exhibit nonholonomic constraints when walking in open spaces, the humanoid steering behavior is modeled as a differential-drive wheeled robot (DDR). The obtained paths are made of geometric primitives that are the shortest in distance in free spaces. The footprints around the path and the positions of the landmarks to which the gaze must be directed are used within a stack-of-tasks (SoT) framework to compute the whole-body motion of the humanoid. We provide some experiments that verify the effectiveness of the proposed strategy on the HRP-2 platform.

scholarly journals A hierarchical approach for rigid-body dynamics model simplification of a high-speed parallel robot by considering kinematics performance

2021 ◽  
Vol 104 (4) ◽  
pp. 003685042110630
Author(s):  
Jinlu Ni ◽  
Jiangping Mei ◽  
Weizhong Hu
Keyword(s):  
Rigid Body ◽  
Trajectory Planning ◽  
High Speed ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Rigid Body Dynamics ◽  
Model Simplification ◽  
Hierarchical Approach ◽  
Dynamics Model ◽  
Body Dynamics

Considering the real-time control of a high-speed parallel robot, a concise and precise dynamics model is essential for the design of the dynamics controller. However, the complete rigid-body dynamics model of parallel robots is too complex for online calculation. Therefore, a hierarchical approach for dynamics model simplification, which considers the kinematics performance, is proposed in this paper. Firstly, considering the motion smoothness of the end-effector, trajectory planning based on the workspace discretization is carried out. Then, the effects of the trajectory parameters and acceleration types on the trajectory planning are discussed. But for the fifth-order and seventh-order B-spline acceleration types, the trajectory will generate excessive deformation after trajectory planning. Therefore, a comprehensive index that considers both the motion smoothness and trajectory deformation is proposed. Finally, the dynamics model simplification method based on the combined mass distribution coefficients is studied. Results show that the hierarchical approach can guarantee both the excellent kinematics performance of the parallel robot and the accuracy of the simplified dynamics model under different trajectory parameters and acceleration types. Meanwhile, the method proposed in the paper can be applied to the design of the dynamics controller to enhance the robot's performance.

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