Abstract
To help hemiplegic patients with stroke to restore impaired or lost upper extremity functionalities efficiently, the design of upper limb rehabilitation robotics which can substitute human practice becomes more important. The aim of this work is to propose a powered exoskeleton for upper limb rehabilitation based on a wheelchair in order to increase the frequency of training and reduce the preparing time per training. This paper firstly analyzes the range of motion (ROM) of the flexion/extension, adduction/abduction, and internal/external of the shoulder joint, the flexion/extension of the elbow joint, the pronation/supination of the forearm, the flexion/extension and ulnar/radial of the wrist joint by measuring the normal people who are sitting on a wheelchair. Then, a six-degree-of-freedom exoskeleton based on a wheelchair is designed according to the defined range of motion. The kinematics model and workspace are analyzed to understand the position of the exoskeleton. In the end, the test of ROM of each joint has been done. The maximum error of measured and desired shoulder flexion and extension joint angle is 14.98%. The maximum error of measured and desired elbow flexion and extension joint angle is 14.56%. It is acceptable for rehabilitation training. Meanwhile, the movement of drinking water can be realized in accordance with the range of motion. It demonstrates that the proposed upper limb exoskeleton can also assist people with upper limb disorder to deal with activities of daily living. The feasibility of the proposed powered exoskeleton for upper limb rehabilitation training and function compensating based on a wheelchair is proved.
1. Introduction
Upper extremity motor function disorder is one of the most common rehabilitation problems of hemiplegic patients with stroke [1]. The upper extremity motor function plays a key role in self-care and social activities. The upper extremity motor function disorder significantly lowers the life quality of hemiplegic patients with stroke [2, 3]. Due to the complex structure and functional requirement of the upper limb, the rehabilitation process of the impaired upper extremity functionality is a long and slow process. Because of the specificity of hemiplegic patients in diagnosis, treatment, and rehabilitation, it brings a series of severe psychological and financial stress for patients [4]. The outcome of upper limb motor rehabilitation depends on duration, intensity and task orientation of the training. The therapists assisting patients have to bear a significant burden. As a result, the duration of primary upper limb rehabilitation is becoming shorter [5]. To deal with these problems, robotic rehabilitation devices with the ability to conduct repetitive tasks and provide assistive force have been proposed.
The upper limb rehabilitation robots can be divided into two types according to the service environment. One is mainly used in the hospital and shared by several patients. The upper limb rehabilitation robots used in the hospital are often designed for rehabilitation training and difficult to move. Loris et al. introduced a dual exoskeleton robot called automatic recovery arm motility integrated system. The system was developed to enable therapists to define and apply patient-specific rehabilitation exercises with multidisciplinary support by neurologist, engineers, ICT specialists and designers [6]. Farshid et al. presented the GENTLE/S system for upper limb rehabilitation. The system comprised a 3-degree-of-freedom (DOF) robot manipulator with an extra 3 DOFs passive gimbal mechanism, an exercise table, computer screen, overhead frame, and chair [7]. Dongjin Lee et al. proposed a clinically relevant upper-limb exoskeleton that met the clinical requirements. The pilot test showed that the safety for robot-aided passive training of patients with spasticity could be guaranteed [8]. The other is mainly used in the home to assist a single patient in activities of daily living. A lightweight and ergonomic upper-limb rehabilitation exoskeleton named CLEVER ARM was proposed by Zeiaee et al. The wearable upper limb exoskeleton was to provide automated therapy to stroke patients [9]. Feiyun et al. presented a seven DOFs cable-driven upper limb exoskeleton for post-stroke patients. The experimental results showed that the activation levels of corresponding muscles were reduced by using the 7 DOFs cable-driven upper limb exoskeleton in the course of rehabilitation [10]. In fact, the main function of upper extremity rehabilitation devices is to provide the physical training and assist the patients with hemiplegia to perform the activities of daily living. However, hospital or home used rehabilitation robot research has just focused on one respect. Indeed, the research on the upper extremity rehabilitation devices would focus on both aspects of assisting and training. Therefore, it is important for the design of upper limb rehabilitation robot to combine the rehabilitation training and assisting function.
The stationary upper extremity rehabilitation robot cannot solve the movability problem and perform the activities of daily living (ADL). The wearable exoskeleton devices are limited by the weight. In addition, whether the range of motion is in line with the physiological joints directly determines the rehabilitation effect. Therefore, the key questions can be summarized as follows. Can we transform the weight of the upper limb exoskeleton to another movable device instead of wearing by patients? How to guarantee the design of upper limb exoskeleton joint axis in line with the human joint movement axis?
To deal with the above questions, some researchers have made useful explorations. Kiguchi et al. proposed a mechanism and control method of a mobile exoskeleton robot based on a wheelchair for 3 DOFs upper-limb motion assist [11]. The first problem of transforming weight can be solved by design based on a wheelchair. The physical rehabilitation training can be realized on a wheelchair instead of a stationary place. The ADL can be assisted by the powered upper limb exoskeleton on a moving platform. However, the rotation axis of each joint (shoulder joint and elbow joint) is moving with the movement of the upper limb. The gap between the exoskeleton and human arm is also changing by following their movement. It does not consider the problem about the movement consistency of the exoskeleton joint rotation axis and the human joint. As for this problem, Vitiello et al. proposed an elbow exoskeleton with double-shelled links to allow an ergonomic physical human-robot interface and a four-degree-of-freedom passive mechanism to allow the user’s elbow and robot axes to be constantly aligned during movement [12]. However, it focused on the elbow. The whole upper limb rehabilitation was not considered. In this work, we present a novel solution for the two mentioned problems. The range of motion of the upper extremity exoskeleton based on a wheelchair is defined through the normal people test. The 6 DOFs exoskeleton based on a wheelchair is designed according to the defined range of motion. The pursuit movement experiment and the assistive movement of drinking water of the prototype are done to verify the feasibility of the design.
2. Materials and Methods
2.1. Definition of ROM of Each Joint for the Specific Upper Limb Exoskeleton on a Wheelchair
To ensure the safety of using an upper limb exoskeleton on a wheelchair, it is necessary to know the ROM of the human upper limb on the wheelchair.
The parts of the upper limb taken into account in the design of an exoskeleton are shoulder, arm, elbow, wrist, and hand. Hand is excluded in an entire upper extremity exoskeleton design because of its complexity and dexterous characteristic. Therefore, this work only analyzes the ROM of the shoulder joint, elbow joint, and wrist joint. And then the upper limb exoskeleton designed in this paper must conform to the ROM of these joints.
2.1.1. Apparatus
The apparatus consists of a wheelchair and a motion analysis system. The motion analysis system can transmit data in real time. It was made in JIANGSU NEUCOGNIC MEDICAL CO., LTD. The system can measure the ROM of the shoulder joint, elbow joint and wrist joint of a person who sits on a common wheelchair. In Figure 1, there are two inertial sensors located at the upside and downside of backbone, and ten inertial sensors located at the upper limb (shoulder, upper arm, forearm, palm, and hand), respectively. All of the sensors in this system can measure the angles in x-, y– and z-axis. Sensor 1 and Sensor 4 are utilized to measure the ROM of the rear waist as the referring data. Sensor 4 and Sensor 6 are utilized to measure the ROM of the shoulder joint as the referring data. Sensor 6 and Sensor 7 are utilized to measure the ROM of the elbow joint as the referring data. Sensor 7 and hand sensor are utilized to measure the ROM of wrist joint as the referring data.[…]
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TBI Rehabilitation 