Development of an End-Effector Type Therapeutic Robot with Sliding Mode Control for Upper-Limb Rehabilitation

Geriatric disorders, strokes, spinal cord injuries, trauma, and workplace injuries are all prominent causes of upper limb disability. A two-degrees-of-freedom (DoFs) end-effector type robot, iTbot (intelligent therapeutic robot) was designed to provide upper limb rehabilitation therapy. The non-linear control of iTbot utilizing modified sliding mode control (SMC) is presented in this paper. The chattering produced by a conventional SMC is undesirable for this type of robotic application because it damages the mechanical structure and causes discomfort to the robot user. In contrast to conventional SMC, our proposed method reduces chattering and provides excellent dynamic tracking performance, allowing rapid convergence of the system trajectory to its equilibrium point. The performance of the developed robot and controller was evaluated by tracking trajectories corresponding to conventional passive arm movement exercises, including several joints. According to the results of experiment, the iTbot demonstrated the ability to follow the desired trajectories effectively

Tracking human upper-limb movements with sliding mode control type-II fuzzy logic

© 2016 IEEE. A knowledge of human upper-limb structure and its mechanical functions are important for developing an exoskeleton. The Sliding Mode Control with Fuzzy Type-II is proposed to control the movements of the human extremity joints. The Lagrange method is used to model the dynamics system of human upper-limb. The findings demonstrate the effectiveness of the proposed controller in tracking the desired motion and it is also able to eliminate the chattering problem as well as deal with uncertainties

Development and Control of a 3-DoF Exoskeleton Robot for Forearm and Wrist Rehabilitation

The research conducted under this project directly contributes to the development of a forearm and wrist rehabilitation robot (UWM-FWRR). Upper extremity impairment following stroke, trauma, sports injuries, occupational injuries, spinal cord injuries, and orthopaedic injuries results in significant deficits in hand manipulation and the performance of everyday tasks. Strokes affect nearly 800,000 people in the United States each year. Rehabilitation programs are the main method of promoting functional recovery in individuals with finger impairment. The conventional therapeutic approach requiring a long commitment by both the clinician and the patient. Robotic devices (RDs) are novel and rapidly expanding technologies in hand rehabilitation. However, existing RDs have not been able to fully restore hand functionality as they cannot provide the independent joint control and levels of velocity and torque required. Our customer discovery [1] reveals that therapists often prescribe therapeutic devices for passive arm/leg movement assistance but no therapeutic devices exist for combined hand, wrist, and forearm movements that can be used at home/clinic. Regaining hand strength and mobility plays an important role in supporting essential activities of daily living, such as eating, and thus has the potential to improve the physical and mental status of both stroke patients and their family caregivers. Therefore, through this research author has develop UWM-FWRR that can provide rehabilitative exercises for forearm and, wrist movements. In contrast to existing RDs, developed UWM-FWRR is a portable, light weight, low cost, and novel powered rehabilitation device that will be developed to provide therapeutic exercises to a wide group of patients with different degrees of impairments. This innovation provides an opportunity for the patients to perform exercises not only with the guidance of a therapist at clinic but also be used at home as a telerehabilitation device through smartphone application (Future works)

Nonlinear control of an exoskeleton seven degrees of freedom robot to realize an active and passive rehabilitation tasks

This doctoral thesis proposes the developments of an exoskeleton robot used to rehabilitate patients with upper-limb impairment, named ETS-MARSE robot. The developments included in this work are the design, and validation of a kinematic inverse solution and nonlinear control strategy for an upper limb exoskeleton robot. These approaches are used in passive and active rehabilitation motion in presence of dynamics and kinematics uncertainties and unexpected disturbances. Considering the growing population of post-stroke victims, there is a need to improve accessibility to physiotherapy by using the modern robotic rehabilitation technology. Recently, rehabilitation robotics attracted a lot of attention from the scientific community since it is able to overcome the limitations of conventional physical therapy. The importance of the rehabilitation robot lies in its ability to provide intensive physiotherapy for a long period time. The measured data of the robot allows the physiotherapist to accurately evaluate the patient’s performance. However, these devices are still part of an emerging area and present many challenges compared to the conventional robotic manipulators, such as the high nonlinearity, dimensional (high number of DOFs) and unknown dynamics (uncertainties). These limitations are provoked due to their complex mechanical structure designed for human use, the types of assistive motion, and the sensitivity of the interaction with a large diversity of human wearers. As a result, these conditions make the robot system vulnerable to dynamic uncertainties and external disturbances such as saturation, friction forces, backlash, and payload. Likewise, the interaction between human and the exoskeleton make the system subjected to external disturbances due to different physiological conditions of the subjects like the different weight of the upper limb for each subject. During a rehabilitation movement, the nonlinear uncertain dynamic model and external forces can turn into unknown function that can affect the performance of the exoskeleton robot. The main challenges addressed in this thesis are firstly to design a human inverse kinematics solution to perform a smooth movement similar to natural human movement (human-like motion). Secondly, to develop controllers characterized by a high-level of robustness and accuracy without any sensitivity to uncertain nonlinear dynamics and unexpected disturbances. This will give the control system more flexibility to handle the uncertainties and parameters’ variation in different modes of rehabilitation motion (passive and active)

Development of an exoskeleton robot for upper-limb rehabilitation

To assist or rehabilitate individuals with impaired upper-limb function, we have developed an upper-limb exoskeleton robot, the ETS-MARSE (motion assistive robotic-exoskeleton for superior extremity). The MARSE is comprised of a shoulder motion support part, an elbow and forearm motion support part, and a wrist motion support part. It is designed to be worn on the lateral side of the upper limb in order to provide naturalistic movements of the shoulder (i.e., vertical and horizontal flexion/extension, and internal/external rotation), elbow (i.e., flexion/extension), forearm (i.e., pronation/supination), and wrist joint (i.e., radial/ulnar deviation, and flexion/extension). This thesis focuses on the modeling, design (mechanical and electrical components), development, and control of the developed MARSE. The proposed MARSE was modeled based on the upper-limb biomechanics; it has a relatively low weight, an excellent power/weight ratio, can be easily fitted or removed, and is able to effectively compensate for gravity. Moreover, to avoid complex cable routing that could be found in many exoskeleton systems, a novel power transmission mechanism was introduced for assisting shoulder joint internal/external rotation and for forearm pronation/supination. The exoskeleton was designed for use by typical adults. However, provisions are included for link length adjustments to accommodate a wide range of users. The entire exoskeleton arm was fabricated primarily in aluminum except the high stress joint sections which were fabricated in mild steel to give the exoskeleton structure a relatively light weight. Brushless DC motors (incorporated with Harmonic Drives) were used to actuate the developed MARSE. The kinematic model of the MARSE was developed based on modified Denavit-Hartenberg notations. In dynamic modeling and control, robot parameters such as robot arm link lengths, upper-limb masses, and inertia, are estimated according to the upper limb properties of a typical adult. Though the exoskeleton was developed with the goal of providing different forms of rehab therapy (namely passive arm movements, active-assisted therapy, and resistive therapy), this research concentrated only on passive form of rehabilitation. Passive arm movements and exercises are usually performed slowly compared to the natural speed of arm movement. Therefore, to control the developed MARSE, a computationally inexpensive a PID controller and a PID-based compliance controller were primarily employed. Further, realizing the dynamic modeling of human arm movement which is nonlinear in nature, a nonlinear computed torque control (CTC) and a modified sliding mode exponential reaching law (mSMERL) techniques were employed to control the MARSE. Note that to improve transient tracking performance and to reduce chattering, this thesis proposed the mSMERL, a novel nonlinear control strategy that combined the concept of boundary layer technique and the exponential reaching law. The control architecture was implemented on a field-programmable gate array (FPGA) in conjunction with a RT-PC. In experiments, typical rehabilitation exercises for single and multi joint movements (e.g., reaching) were performed. Experiments were carried out with healthy human subjects where trajectories (i.e., pre-programmed trajectories recommended by therapist/clinician) tracking the form of passive rehabilitation exercises were carried out. This thesis also focused on the development of a 7DoFs upper-limb prototype (lower scaled) ‘master exoskeleton arm’ (mExoArm). Furthermore, experiments were carried out with the mExoArm where subjects (robot users) operate the mExoArm (like a joystick) to maneuver the MARSE to provide passive rehabilitation. Experimental results show that the developed MARSE can effectively perform passive rehabilitation exercises for shoulder, elbow and wrist joint movements. Using mExoArm offers users some flexibility over pre-programmed trajectories selection approach, especially in choosing range of movement and speed of motion. Moreover, the mExoArm could potentially be used to tele-operate the MARSE in providing rehabilitation exercises

Study on control of a robotic orthosis actuated by pneumatic artificial muscle for gait rehabilitation

芝浦工業大学2019年

Nonlinear control of a seven degrees-of-freedom exoskeleton robot arm

Advances in the field of robotics have allowed increasingly integrating robotic devices for rehabilitation of physical disabilities. This research work is encompassed into the field of rehabilitation robotics; it presents the development of the robot ETS-MARSE, a seven degrees-of-freedom exoskeleton designed to be worn in the human arm. The developments include the study and implementation of a relatively novel nonlinear control approach, as well as different rehabilitation schemes. One of the characteristics of a rehabilitation robot is that it deals with a wide number of patients that have different biomechanical and physiological conditions. The implementation of the nonlinear control technique known as Virtual Decomposition Control addresses this issue with its internal parameters’ adaptation that presents a robust behavior to different characteristics of the robot users. Besides, this technique simplifies the complexity of high degree-of-freedom robots by its innovative sub-systems decomposition. All of above, while ensuring the system asymptotic stability and excellent trajectory tracking. Between the different rehabilitation schemes, we can mention: passive, active-assistive and active rehabilitation. The first one follows predefined trajectories and relies on the efficiency of the controller. The two other schemes require understanding the user’s intention of movement and take an action in order to guide, restrain, correct or follow it. For this purpose, we present an approach that utilizes a force sensor as the human-robot interface in order to transform, via an admittance function, the forces that the user exert to the robot end-effector (handle), and execute active-assisted or active rehabilitation. Finally among the main developments of this work, an approach is presented in which the need of a force sensor to perform some active rehabilitation tasks is removed. By means of a nonlinear observer, the interaction forces are estimated and the user’s intention of movement followed. Experimental results show the effectiveness of all the proposed approaches. All the tests involving humans were tested with healthy subjects. Trajectory tracking of the robot is executed in joint space; some trajectories are given in Cartesian space and transformed to joint space by means of the pseudoinverse of the Jacobian technique. However this option is limited; a mandatory next step to improve many functionalities of the robot is to solve its inverse kinematics. Between other progresses that are in development, is an approach to process electromyographic signals in order to obtain information from the robot’s users. First results on this methodology are presented. Teleoperation and haptic capabilities are also in the initial stage of development

Impact of Ear Occlusion on In-Ear Sounds Generated by Intra-oral Behaviors

We conducted a case study with one volunteer and a recording setup to detect sounds induced by the actions: jaw clenching, tooth grinding, reading, eating, and drinking. The setup consisted of two in-ear microphones, where the left ear was semi-occluded with a commercially available earpiece and the right ear was occluded with a mouldable silicon ear piece. Investigations in the time and frequency domains demonstrated that for behaviors such as eating, tooth grinding, and reading, sounds could be recorded with both sensors. For jaw clenching, however, occluding the ear with a mouldable piece was necessary to enable its detection. This can be attributed to the fact that the mouldable ear piece sealed the ear canal and isolated it from the environment, resulting in a detectable change in pressure. In conclusion, our work suggests that detecting behaviors such as eating, grinding, reading with a semi-occluded ear is possible, whereas, behaviors such as clenching require the complete occlusion of the ear if the activity should be easily detectable. Nevertheless, the latter approach may limit real-world applicability because it hinders the hearing capabilities.</p

Controller design of a robotic orthosis using sinusoidal-input describing function model

Stroke is one of top leading causes of death in the world and it happens to more than 15 million people yearly. According to the National Stroke Association of Malaysia (NASAM), stroke is the third leading cause of death in Malaysia with around 40,000 cases reported annually. Forty percent of stroke survivors suffer from movement impairments after stroke. My grandfather was one of the victims and he was unable to attend any rehabilitation sessions due to several reasons. Hence, he lost the golden time to regain his movement and freedom. There are a lot of similar cases that happen daily in Malaysia. Besides, as the number of stroke patients increases yearly, the need for physiotherapists or rehabilitation machines equally increases. Hence, a low-cost clinical rehabilitation device is essential to provide assistance for an effective rehabilitation program and substitute the conventional method, as well as to reduce the burden of physiotherapists. In future, the proposed rehabilitation device would benefit not only stroke patients, but any patients who lost their normal walking ability including post-accident patients or those who suffer from spinal cord injury. The rehabilitation device aims to provide training assistance to patients not only in rehabilitation centres but also at home for daily training. The robotic orthosis is planned to be configured based on moving joint angles of human lower extremities. In the first stage of this research, angle-time characteristics for knee and hip swinging motion are utilised as a sagittal motion reference for the rehabilitation devices. The aim of following a proper gait cycle during rehabilitation training is to train patients to perform standing and swinging phases at proper timing and simultaneously provide the correct position reference to the patient during rehabilitation training. This can prevent patients from walking abnormally with an asymmetric gait cycle along or after the rehabilitation program. Besides, various limitations and the bulky structure of other rehabilitation devices lead to the design of the two-link lower limb rehabilitation device. This project aims to develop an assistive robotic rehabilitation device that generates a human gait trajectory for hemiplegic stroke patient gait rehabilitation in future. The shortcomings of other control applications due to environmental conditions and disturbances lead to the implementation of the describing function approach in the development of the devices. A sinusoidal-input describing function (SIDF) approach was implemented to linearize the nonlinear robotic orthosis with linear transfer function. The reason for utilising the SIDF approach is due to the nonlinear actual plant model with the present of load torque disturbances, discontinuous nonlinearities such as saturation and backlash, and also multivariable in the system. The nonlinear properties of the plant were proven in the preliminary stage of the research. A conventional controller, PID control combined with position and trajectory inputs were also applied to the system in the early stage of research. However, the experimental results were not satisfying. Finally, the SIDF approach was chosen to linearize the nonlinear system. Hence, generating a controller is much easier with a linear model of the nonlinear system. A SIDF approach was implemented to generate a controller for the multivariable, nonlinear closed loop system. Firstly, the SIDF approach enables the determination of the linear function of the nonlinear model known as the SIDF model. By utilising the linear model to mimic the behaviour of the nonlinear rehabilitation system, the controller for the nonlinear plant was able to be generated. In this research a controller based on linear control theory technique was used. The MATLAB library was used to design the lead-lag controller for the rehabilitation device. Various simulations such as step responses, tracking and decoupling of both links were performed on the generated controller with the nonlinear model to study the capability of the controller. Besides that, real life experiment testing was carried out to validate the feasibility of the controller designed via the SIDF approach. Simulation and experimental results were obtained, compared, and discussed. The highly accurate responses gained from experimental setup showed the robustness of the controller generated via SIDF approach. The implementation of the SIDF approach in a rehabilitation device (vertical two-link manipulator) is a first and hence, fulfils a novelty requirement for this research