XueJun Jin

Upper Limb Rehabilitation Using a Planar Cable-Driven Parallel Robot with Various Rehabilitation Strategies

Robotic technology became an important tool for rehabilitation especially for stroke patients. This paper presents development of three degrees-of-freedom cable-driven parallel robot (CDPR) for upper limb rehabilitation. Main features of the proposed rehabilitation robot are to provide relatively large workspace and to be less dangerous especially in the situation of robot’s malfunction owing to its reduced inertia of a moving part. In addition, the cable-driven rehabilitation robot has many advantages such as transportability, low cost, low actuation power, safeness, large workspace and so on. In this paper, we analyzed the patient’s joint movement during the passive rehabilitation using the developed CDPR. In addition, the paper presents the several types of rehabilitation therapy strategies and their implementation using the proposed CDPR system.

Open-loop position control of a polymer cable–driven parallel robot via a viscoelastic cable model for high payload workspaces

A polymer cable–driven parallel robot has a wide range of potential industrial applications by virtue of its light actuator dynamics, high payload capability, and large workspace. However, due to a viscoelastic behavior of polymer cable and difficulty in actual cable length measurement, there have been inevitable position and tracking control accuracy problems such as pick and place a high payload application. In this article, to overcome control problem, we propose a model-based open-loop control with the cable elongation compensation via experimentally driven cable model and switching control logic without additional Cartesian space feedback signal. The approach suggests a five-element cable model that is made with series combination of a linear spring and two Voigt models as a function of payload and cable length that are available to be measured in real-time. Experimental results show that using the suggested method, the cable length error due to viscoelastic effect can be compensated, and thus the position control accuracy of the polymer cable–driven parallel robot improved remarkably especially in gravity direction.

Workspace analysis of upper limb for a planar cable-driven parallel robots toward upper limb rehabilitation

Nowadays robotic technology is widely used in rehabilitation especially in stroke rehabilitation. Comparing conventional robots, cable-driven parallel robots have many advantages such as low moving inertia, high power efficiency, large workspace, low cost, and so forth. On this account, three-degree-of-freedom (3-DOF) cable-driven parallel for upper limb rehabilitation is currently under development. This paper presents motion analysis of upper limb to design a 3-DOF upper limb rehabilitation robot. Main feature of this rehabilitation robot is to provide the relatively large workspace and to be less dangerous in the situation of robots malfunction due to reduced moving part. Since our rehabilitation is being designed to have a planar workspace, the motion of upper limb is also analyzed in a plane.

A Polymer Cable Creep Modeling for a Cable-Driven Parallel Robot in a Heavy Payload Application

A polymer cable driven parallel robot can be an effective system in many fields due to its fast dynamics, high payload capability and large workspace. However, creep behavior of polymer cables may yield a posture control problem, especially in high payload pick and place application. The aim of this paper is to predict creep behavior of polymer cables by using different mathematical models for loading and unloading motion. In this paper, we propose a five-element model of the polymer cable that is made with series combination of a linear spring and two Voigt models, to portray experimental creep in simulation. Ultimately, the cable creep can be represented by payloads and cable length estimated according to the changes of actual payloads and cable lengths in static condition.

Geometric Parameter Calibration for a Cable-Driven Parallel Robot Based on a Single One-Dimensional Laser Distance Sensor Measurement and Experimental Modeling

A cable-driven parallel robot has benefits of wide workspace, high payload, and high dynamic response owing to its light cable actuator utilization. For wide workspace applications, in particular, the body frame becomes large to cover the wide workspace that causes robot kinematic errors resulting from geometric uncertainty. However, appropriate sensors as well as inexpensive and easy calibration methods to measure the actual robot kinematic parameters are not currently available. Hence, we present a calibration sensor device and an auto-calibration methodology for the over-constrained cable-driven parallel robots using one-dimension laser distance sensors attached to the robot end-effector, to overcome the robot geometric uncertainty and to implement precise robot control. A novel calibration workflow with five phases—preparation, modeling, measuring, identification, and adjustment—is proposed. The proposed calibration algorithms cover the cable-driven parallel robot kinematics, as well as uncertainty modeling such as cable elongation and pulley kinematics. We performed extensive simulations and experiments to verify the performance of the suggested method using the MINI cable robot. The experimental results show that the kinematic parameters can be identified correctly with 0.92 mm accuracy, and the robot position control accuracy is increased by 58%. Finally, we verified that the developed calibration sensor devices and the calibration methodology are applicable to the massive-size cable-driven parallel robot system.

Geometric parameter calibration using a low cost laser distance sensor for a planar cable robot: MATLAB simulation

This paper proposes a calibration algorithm for a three degrees-of-freedom (DOF) planar cable-driven parallel robot. The developed calibration algorithm uses a low-cost laser distance sensor to measure the distance between an end-effector and a laser reflector, and also uses the cable lengths measured by using motor encoders. MATLAB simulation results show that using a single laser distance sensor we can calibrate the planar cable robot accurately, and also that selection of the desired end-effector poses influences the calibration accuracy.