Current Robotics Reports (2020) 1:131–144 https://doi.org/10.1007/s43154-020-00015-4 REHABILITATION AND ASSISTIVE ROBOTICS (M RAISON AND S ACHICHE, SECTION EDITORS) Human-Robot Interaction in Rehabilitation and Assistance: a Review Abolfazl Mohebbi1 Published online: 11 August 2020 # Springer Nature Switzerland AG 2020 Abstract Purpose of Review Research in assistive and rehabilitation robotics is a growing, promising, and challenging field emerged due to various social and medical needs such as aging populations, neuromuscular, and musculoskeletal disorders. Such robots can be used in various day-to-day scenarios or to support motor functionality, training, and rehabilitation. This paper reflects on the human-robot interaction perspective in rehabilitation and assistive robotics and reports on current issues and developments in the field. Recent Findings The survey on the literature reveals that new efforts are put on utilizing machine learning approaches alongside novel developments in sensing technology to adapt the systems with user routines in terms of activities for assistive systems and exercises for rehabilitation devices to fit each user’s need and maximize their effectiveness. Summary A review of recent research and development efforts on human-robot interaction in assistive and rehabilitation robotics is presented in this paper. First, different subdomains in assistive and rehabilitation robotic research are identified, and accord- ingly, a survey on the background and trends of such developments is provided. Keywords Human-robot interaction . Artificial intelligence . Human-centered design . Feedback control system . Assistive . Rehabilitation robotics Introduction active prosthetics or exoskeletons for assisting different sen- sorimotor functions such as arm, hand, leg, ankle [3, 4•]. Rehabilitation robotics is a research field focused on augment- With fast-growing technological developments in artificial ing and analyzing rehabilitation procedures by using robotic intelligence, sensing, computation and processing, prototyping, systems. Such systems are developed to aid various methods and fabrication, an increasing number of research efforts have of therapeutic training and assessment of sensorimotor perfor- been recently focused on assistive and rehabilitation robotics due mance [1]. Robotic rehabilitation has been very well received to their vast capabilities in rehabilitating and empowering users. by both patients and clinical professionals and has been found This corresponds to the significant social needs such as motion to be an effective method for motor function therapy in motor aids for the elderly or assisting patients with motor impairments, impairment patients such as stroke [2]. Assistive robotics, on as well as worker augmentation in the industry dealing with the other hand, aims at providing support to patients with intensive physical duties [5, 6]. Moreover, such robotic platforms disabilities to perform their activities of daily living (ADLs) can provide support to users by correcting or preventing unde- with more independence. Examples are moving, grasping, and sired motions, extending the range of motion and workspace, handling objects, eating, etc. Often, a robotic system can be adding extra load-bearing, and incorporating specific force and purposed for both rehabilitation and assisting. For example, motion control capabilities [7]. A majority of previous designs for assistive and rehabilitation robots are functional in terms of delivering the required outputs and performing desired tasks, but This article belongs to the Topical Collection on Rehabilitation and their efficiency is in question due to not using the state-of-the-art Assistive Robotics technologies, and also incorporating insufficient knowledge about the human user during the design and control conception * Abolfazl Mohebbi [8]. Hence, a human-centric approach in design is needed that [email protected] considers various aspects such as the human neural and muscu- 1 Department of Mechanical Engineering, Polytechnique Montréal, loskeletal system and primarily it calls for a focus on human- C.P. 6079, succ. Centre-ville, Montreal, QC H3C 3A7, Canada robot interaction (HRI) and interface technologies [9]. 132 Curr Robot Rep (2020) 1:131–144 Human-robot interaction is currently a very extensive and react and adapt [21]. The assistive robotics, on the other hand, diverse field of research dedicated to understanding, design- cover a broad range of systems, from assistive robots for ma- ing, and evaluating robotic systems for use by or with humans nipulation and mobility that provide support to patients with either in their physical proximity or remotely [10]. An HRI motor function deficits [22], to wearable robots that physically problem is essentially understanding and shaping the interac- augment the body [23], or social assistive robots that aid in tions between humans and robots by assessing the capabilities education and cognitive rehabilitation [24]. of both sides and designing the technologies that form suitable This review paper describes surveys new developments in interactions. This constitutes a multidisciplinary field of re- different categories of rehabilitation and assistive robotics search where various fields such as cognitive sciences, medi- with a focus on state-of-the-art human-robot interaction ac- cine, engineering, and design come together [11]. cording to each category. Various aspects and domains are Robots use the various sensor information to perceive often involved in the development of HRI systems such as humans in the environment they co-exist in. Significant re- design, prototyping, fabrication, sensing technology, commu- search and development efforts exist in the literature on sens- nications, control, etc. Although covering all of these subjects ing components and software for extracting the human kine- is out of the scope of this paper and we intend to mostly cover matics. Depth cameras, stereo-vision devices, infrared, and the soft aspects of HRI in rehabilitation and assistive robotics laser range-finders are examples of the sensing technologies which are the sensory modalities, feedback control ap- used for motion tracking and kinematic assessment of the proaches, and intelligent algorithms. Five search directories human and the environment [12]. The proprioception sensors were utilized in this search strategy and were chosen for their enable the robots to have information over their own move- content and relevance to the HRI approaches in assistive mo- ment and positional state relative to a reference frame. These bile robots, assistive manipulators, robotic prostheses and or- sensing units include encoders, potentiometers, inertial mea- thoses, and rehabilitation robotics. They were from Ei surement units (IMUs), and accelerometers [13]. Moreover, Compendex, Web of Science, PubMed, Proquest, and force and torque sensors are used to measure interaction Science-Direct. Abstract and full texts were then assessed, forces, torques, pressures, and mechanical stress [14]. Tactile and peer reviewed by the author for direct relevance to the sensing units and pressure arrays are used to create a sense of topic and scope of this study. A total of 91 relevant papers touch for the robot with respect to the environment and users were discovered from papers restricted to the last 5 years. [15]. On the communication level, speech recognition algo- Figure 1 shows the distribution of the reviewed papers used rithms are used to interpret human intentions or commands in each category. through speech and vocal signals. In this regard, natural lan- This paper is organized as follows; “Assistive Mobile guage processing (NLP) is concerned with understanding the Robots” describes the HRI in assistive mobile robots such as interactions between computers and human languages smart wheelchairs and walkers; “Assistive Robotic through tools such as neural network architectures and learn- Manipulators” reviews HRI developments for assistive robot- ing algorithms [16]. ic manipulators; “Robotic Prostheses” is dedicated to robotic Based on the therapeutic and clinical techniques, rehabili- prostheses and their interaction with users; “Robotic tation robots are designed to improve and determine the adapt- Exoskeletons” describes current issues and developments of ability level of patients. In the first category of rehabilitation HRI for robotic orthoses and exoskeletons, and finally, robots, simple positional control of extremities is practiced for “Rehabilitation Robots” provides insights about various as- a passive exercise where the robot is used in a positional pects of HRI in rehabilitation robotics. Concluding remarks trajectory mode which does not involve the active participa- are also provided at the end. tion of a patient on either neuromuscular or sensory levels [17]. The second category of such robots incorporates active assisted exercises, in which the robot moves the patient’sex- Assistive Mobile Robots tremity, e.g., leg, arm, etc., along a predetermined trajectory without any force applied to keep the motion on track [18]. In Applying mobile robotic concepts on assistive devices has the third category, active constrained exercises are utilized been an active research area for over two decades and corre- where the robot applies an opposing force if the extremity sponds to two main applications: smart wheelchair systems moves outside of a predefined path or a 3D virtual space and assistive robotic walkers.