Kinematic Modeling and Control of Robot Manipulators via Unit Quaternions: Application to a Spherical Wrist

Abstract This article presents a novel kinematic model and controller design for a mobile robot with four Centered Orientable Conventional (COC) wheels. When compared to non-conventional wheels, COC wheels perform better over rough terrain, are not subject to vertical chatter and offer better braking capability. However, COC wheels are pseudo-omnidirectional and subject to nonholonomic constraints. Several established modeling and control techniques define and control the Instantaneous Center of Rotation (ICR); however, this method involves singular configurations that are not trivial to eliminate. The proposed method uses a novel ICR-based kinematic model to avoid these singularities, and an ICR-based nonlinear controller for one ‘master’ wheel. The other ‘slave’ wheels simply track the resulting kinematic relationships between the ‘master’ wheel and the ICR. Thus, the nonlinear control problem is reduced from 12th to 3rd-order, becoming much more tractable. Simulations with a feedback linearization controller verify the approach.

Download Full-text

Modeling and Control of Robot Manipulators

Industrial Robot the international journal of robotics research and application ◽

10.1108/ir.2000.04927aae.003 ◽

2000 ◽

Vol 27 (1) ◽

Keyword(s):

Robot Manipulators ◽

Modeling And Control ◽

And Control

Download Full-text

Mechanical Design and Kinematic Modeling of a Cable-Driven Arm Exoskeleton Incorporating Inaccurate Human Limb Anthropomorphic Parameters

Sensors ◽

10.3390/s19204461 ◽

2019 ◽

Vol 19 (20) ◽

pp. 4461 ◽

Cited By ~ 1

Author(s):

Weihai Chen ◽

Zhongyi Li ◽

Xiang Cui ◽

Jianbin Zhang ◽

Shaoping Bai

Keyword(s):

Mechanical Design ◽

Kinematic Model ◽

Light Weight ◽

Skeletal System ◽

Kinematic Modeling ◽

Modeling And Control ◽

Arm Rehabilitation ◽

Human Arm ◽

Human Limb ◽

And Control

Compared with conventional exoskeletons with rigid links, cable-driven upper-limb exoskeletons are light weight and have simple structures. However, cable-driven exoskeletons rely heavily on the human skeletal system for support. Kinematic modeling and control thus becomes very challenging due to inaccurate anthropomorphic parameters and flexible attachments. In this paper, the mechanical design of a cable-driven arm rehabilitation exoskeleton is proposed to accommodate human limbs of different sizes and shapes. A novel arm cuff able to adapt to the contours of human upper limbs is designed. This has given rise to an exoskeleton which reduces the uncertainties caused by instabilities between the exoskeleton and the human arm. A kinematic model of the exoskeleton is further developed by considering the inaccuracies of human-arm skeleton kinematics and attachment errors of the exoskeleton. A parameter identification method is used to improve the accuracy of the kinematic model. The developed kinematic model is finally tested with a primary experiment with an exoskeleton prototype.

Download Full-text