Alireza Rastegarpanah

Path planning of the hybrid parallel robot for ankle rehabilitation

This paper presents a new configuration for ankle rehabilitation using a 9-DOF (degree of freedom) hybrid parallel robot. The robot contains nine linear actuators serially connecting two movable platforms and one stationary platform. The optimization is based on the singularity and dynamic analysis of the robot. The obtained data of the ankle motions from a series of experiments were applied to the model in order to investigate the motion of the end-effector and the force required for each actuator in a particular path. The end-effector tracking simulation results validated the proposed theoretical analysis of the required rehabilitation path of the foot.

Lower Limb Rehabilitation Using Patient Data

The aim of this study is to investigate the performance of a 6-DoF parallel robot in tracking the movement of the foot trajectory of a paretic leg during a single stride. The foot trajectories of nine patients with a paretic leg including both males and females have been measured and analysed by a Vicon system in a gait laboratory. Based on kinematic and dynamic analysis of a 6-DoF UPS parallel robot, an algorithm was developed in MATLAB to calculate the length of the actuators and their required forces during all trajectories. The workspace and singularity points of the robot were then investigated in nine different cases. A 6-DoF UPS parallel robot prototype with high repeatability was designed and built in order to simulate a single stride. Results showed that the robot was capable of tracking all of the trajectories with the maximum position error of 1.2 mm.

Towards advanced robotic manipulation for nuclear decommissioning: A pilot study on tele-operation and autonomy

We present early pilot-studies of a new international project, developing advanced robotics to handle nuclear waste. Despite enormous remote handling requirements, there has been remarkably little use of robots by the nuclear industry. The few robots deployed have been directly teleoperated in rudimentary ways, with no advanced control methods or autonomy. Most remote handling is still done by an aging workforce of highly skilled experts, using 1960s style mechanical Master-Slave devices. In contrast, this paper explores how novice human operators can rapidly learn to control modern robots to perform basic manipulation tasks; also how autonomous robotics techniques can be used for operator assistance, to increase throughput rates, decrease errors, and enhance safety. We compare humans directly teleoperating a robot arm, against human-supervised semi-autonomous control exploiting computer vision, visual servoing and autonomous grasping algorithms. We show how novice operators rapidly improve their performance with training; suggest how training needs might scale with task complexity; and demonstrate how advanced autonomous robotics techniques can help human operators improve their overall task performance. An additional contribution of this paper is to show how rigorous experimental and analytical methods from human factors research, can be applied to perform principled scientific evaluations of human test-subjects controlling robots to perform practical manipulative tasks.

Motion Simulation of a Hybrid Parallel Robot for Ankle Rehabilitation

This paper addresses the path planning of a hybrid parallel robot for ankle rehabilitation. The robot contains 3-DOF parallel mechanism that is attached on top of the 6-DOF hexapod. The 6-UPU-3-UPR parallel robot is developed to simulate ankle motions for the rehabilitation of post-stroke patients with an affected ankle. The inverse kinematic of hybrid parallel robot is developed in order to track the end-effector’s position through Matlab software. The calculated stroke size of each actuator is imported to apply the forward kinematic for determining the position of end-effector. The experimental and simulation values of the hexapod are compared with those of the hybrid structure through a number of exercise motion paths. The results reveal that, in general, the simulation values follow well the experimental values, although with different degrees of variation for each of the structures considered.Copyright

Autonomous vision-guided bi-manual grasping and manipulation

This paper describes the implementation, demonstration and evaluation of a variety of autonomous, vision-guided manipulation capabilities, using a dual-arm Baxter robot. Initially, symmetric coordinated bi-manual manipulation based on kinematic tracking algorithm was implemented on the robot to enable a master-slave manipulation system. We demonstrate the efficacy of this approach with a human-robot collaboration experiment, where a human operator moves the master arm along arbitrary trajectories and the slave arm automatically follows the master arm while maintaining a constant relative pose between the two end-effectors. Next, this concept was extended to perform dual-arm manipulation without human intervention. To this extent, an image-based visual servoing scheme has been developed to control the motion of arms for positioning them at a desired grasp locations. Next we combine this with a dynamic position controller to move the grasped object using both arms in a prescribed trajectory. The presented approach has been validated by performing numerous symmetric and asymmetric bi-manual manipulations at different conditions. Our experiments demonstrated 80% success rate in performing the symmetric dual-arm manipulation tasks; and 73% success rate in performing asymmetric dualarm manipulation tasks.

Path’s Slicing Analysis as a Therapist’s Intervention Tool for Robotic Rehabilitation

The assisted limb rehabilitation process is commonly associated with advanced control of the affected limb through robotic assistance and human interference. The robotic element is only expected to be able to reproduce the motion suitable for large variations of patient’s condition within a reasonable accuracy and stiffness. Therapist’s intervention of fine-control is in the format of planar elements (like pelvis linkage) or joints (like knee), which relate to trajectory or orientation adjustments. The rehabilitation process has to consider the patient’s ability, limit and motion constraint that form those two factors. The parameters for controlling these is associated with kinematic, that defines the behaviour and characteristic of the lower limb. The developed 3D Python simulation system allows for this fine-tuning in the form of slice analysis and interval analysis. The results show that Bezier could be successfully used in various development aspects of parallel robots. The Hybrid and Hexapod robot configurations in this study can then be linked to a Haptic controller that runs on Python’s Haptic engine.

Application of a parallel robot in lower limb rehabilitation: A brief capability study

Robotic rehabilitation has a significant potential to reduce the clinical labor costs of physiotherapy. Robotic therapy allows patients to have more in-depth repetitive movements while the therapists evaluate the progress of the recovery. This paper investigates the potential of a 6 degrees of freedom parallel robot, designed and built at the University of Birmingham, for use in robotic rehabilitation of stroke patients. The foot trajectories of eight post-stroke patients were recorded and analyzed in a gait laboratory. A graphical user interface (GUI) has been designed, which enables the physiotherapist to select the desired exercise from a dedicated database. Three different rehabilitation exercises were investigated: hip flexion/extension, ankle dorsiflexion /plantarflexion, and marching. The results show that the robot was able to repeat all of these foot trajectories successfully, while being able to lift 200kg load in its dynamic mode. This suggests that the robot has the capability to successfully deliver lower limb rehabilitation exercises.

Kinematic performance enhancement of wheelchair-mounted robotic arm by adding a linear drive

Wheelchair-Mounted Robotic Arms have been used to help impaired people to reach objects and perform essential activities in an autonomous way. Different available models are presented in this paper and a simple design is proposed to improve the kinematic performances of the integrated system in order to allow the user to increase its capability of interaction with home environment. To this end, a linear drive has been added to the Raptor model in order to move along the wheelchair. The benefit of the proposed development has been proved with a kinematic performance assessment procedure, which has analyzed critical points in the 3D space, providing 26% increase in performance with respect to the existing solution.

Targeting effect on gait parameters in healthy individuals and post-stroke hemiparetic individuals:

Background A targeting effect may occur in any gait analysis trial where the participant is instructed to step in a particular area or a clearly marked target is in their path. The targeting effect may affect the gait parameters and any variability being studied in regard to the participants. There are few studies examining this effect for healthy subjects and none for special populations. Methods This study aimed to investigate if any targeting effects occurred in healthy and stroke-survivor populations. Eight male participants were recruited, four of whom exhibited right-hand side hemiparesis resulting from stroke. Each participant performed a series of gait trials at a comfortable walking pace after being made aware of the force plate in the centre of the walkway. The participants gait was then analysed and compared before and after the target force plate. Results The results of the trials showed significant variations (p < 0.005) in the spatiotemporal gait parameters in both the healthy and stroke-survivor groups indicating a targeting effect. Conclusions The effects were similar in both groups with the step speed and length being slower and shorter for the targeting step compared to the step after the force plate.

Path-planning of a hybrid parallel robot using stiffness and workspace for foot rehabilitation:

Stiffness is one of the important parameters for estimating the performance of hybrid parallel robots as it is not constant throughout its workspace. The aim of this study is to provide an optimum path based on maximum stiffness within the workspace of a 9-degree-of-freedom hybrid parallel mechanism configuration, which includes nine linear actuators connecting one stationary and two moving platforms in series. The proposed robot is designed for ankle rehabilitation, where accurate and precise movement of lower extremities is required. The design takes advantage of two important characteristics of parallel robots: stiffness and workspace. The proposed methodology to determine the stiffness of hybrid robot in three single axes is based on calculation of position vector of each actuator in any particular pose, by considering the inverse kinematics of the system, in order to obtain the magnitude and direction of the applied forces. The results obtained from the workspace calculations have been compared with those of two standard parallel mechanisms including a 6-degree-of-freedom hexapod and a tripod with 3 degrees of freedom. The stiffness of the robot has been calculated in simulation and then compared with those of a developed prototype hybrid model in two different case studies.