The paper describes the development of a passive mechanical lower arm (PMLA) intended for physical human-robot interaction studies. Our research is focused on cooperation of a small industrial robot and human operator where collision is expected only between the robot end-effector and the lower arm of the human worker. A mathematical model of the passive human lower arm was built and adopted for the control of the PMLA. The mathematical model was optimized using the data from the experiments performed with human volunteers and implemented into the control scheme. The experiments with human volunteers were performed with safely low contact forces. The emulation system of the human lower arm was thoroughly evaluated in the robot impact experiments while using plane and line robot end-effector tools. During the experiment the impact force and the impact energy density were measured and compared to the measurements of the investigation with human volunteers. The PMLA proved to be a good emulation system of the passive human lower arm.

Rehabilitation robots, together with vision and audio systems form the multimodal environment for exercising the person in a number of ways, unavoidably influencing the physiological state of the subject. This paper examines viability of measuring psycho physiological responses to different robotic tasks. The heart rate, skin conductance, respiration and peripheral skin temperature were observed to verify if physical activity obstructs useful recordings and to verify responses in stroke population. 30 healthy subjects were checked with a control task, a purely mental task and task with physical load. 23 subacute stroke persons did a control task, pick and place task (+ inverted version) and Stroop test, same as 22 healthy control subjects. Psycho physiological measurements yielded results even in the presence of physical load and can thus potentially be useful for rehabilitation robotics. Similar responses as in healthy control group were found in the stroke group. Skin conductance response frequency, respiratory rate, skin conductance and skin temperature (all changes from baseline) were confirmed as parameters signaling changes in arousal and valence of both, stroke and control groups.

Our work is focused on cooperation of a small industrial robot and human operator where collision is expected only between the robot end-effector and the lower arm of the human worker. To study the effect of the impact between the robot and man, a passive mechanical lower arm (PMLA) was developed. The investigation presented in this paper evaluates whether the PMLA is a sufficiently accurate emulation system of a passive human lower arm. The same experiments were performed with the PMLA and with human volunteers. The results of both investigations were compared and evaluated to determine whether the PMLA can competently replace human volunteers in dangerous future investigations.

In the paper we propose a method for assessment of hand motion which is based on optical tracking system and parametric model of a hand. The model was scaled according to hand external dimensions of each individual. Optical tracking device was used for model validation which was made for middle and index finger. The algorithms for calculation of hinge joint axis of rotation and ball joint center of rotation were employed. The joint angles were obtained in two ways, from known centers of joint rotation and by solving inverse kinematics for finger from given positions of fingertips. The lengths of finger segments, calculated by using data from statistical anthropometry, do not differ notably from the lengths obtained from calculated centers of rotation of joints. The angles obtained by inverse kinematics are comparable to the angles obtained from estimated centers of rotation. Minimalistic approach makes the method suitable for calibration of a sensor glove

The paper presents a robot cell for multimodal standing-up motion augmentation. The robot cell is aimed at augmenting the standing-up capabilities of impaired or paraplegic subjects. The setup incorporates the rehabilitation robot device, functional electrical stimulation system, measurement instrumentation and cognitive feedback system. For controlling the standing-up process a novel approach was developed integrating the voluntary activity of a person in the control scheme of the rehabilitation robot. The simulation results demonstrate the possibility of “patient-driven” robot-assisted standing-up training. Moreover, to extend the system capabilities, the audio cognitive feedback is aimed to guide the subject throughout rising. For the feedback generation a granular synthesis method is utilized displaying high-dimensional, dynamic data. The principle of operation and example sonification in standing-up are presented. In this manner, by integrating the cognitive feedback and “patient-driven” actuation systems, an effective motion augmentation system is proposed in which the motion coordination is under the voluntary control of the user.

In the paper an application of Kalman filter technique in rehabilitation engineering is presented. The functional electrical stimulation (FES) is frequently applied motor augmentation aid in incomplete spinal cord injury that is in a need for modification. Therefore the gait reeducation system was proposed that successfully applies the presented algorithm. The proposed sensory system is equipped with dual-axial accelerometer and a gyro and is placed at the shank of the paretic leg. The data assessed present input into mathematical algorithms applied for shank angle estimation. The algorithm is based on Kalman filter estimating the angle error and correcting the actual measurement. The proposed method was tested during healthy subjects walking on even terrain and treadmill. Afterwards the comparison with optical measurement system Vicon was performed and the triggering of the KES was also tested. Outcome of the measurements clearly shows how sensory integration algorithm may serve the purpose and its precedence over the single sensor applications.

A robot assistive device is presented aimed for training and evaluation of standing-up in impaired people. The robot device is designed as a 3 DOF mechanism supporting the subject under the buttocks. The device is driven by an electrohydraulic servosystem capable to operate in a position or in force control mode. The evaluation of the standing-up assistive device was accomplished in rising trials of a paraplegic subject. In the experiments the position control approach was employed. The results proved that the device can be efficiently used for training and evaluation of standing-up maneuver. Furthermore, an algorithm is proposed which generates the reference value of the man/machine interaction force to be tracked by the robot force controller. The simulation results proved an adequate and robust performance. In this manner, the novel robot device can be utilized in the "robot driven" or the "patient driven" standing-up training.

A robot assistive device is proposed aimed as a support for the impaired individuals when rising from sitting to standing position. The aim of the simple standing-up robot is to impose to the impaired person the reference position trajectory of the pelvis while unloading the upper and lower extremities. Variety of possible utilization areas are feasible: the device can serve as a functional rehabilitative aid, as training device or as an assessment tool when studying the standing-up manoeuvre. As a prototype, the 1-DOF hydraulically driven robot mechanism was built. Initial testing and evaluation results are presented together with the functional electrical stimulation of the paralysed muscles.

We present a kinematic model of a paraplegic subject walking with crutches where the subject with the crutches is modeled as a parallel kinematic structure. The model is employed to investigate if certain quadrupedal gait patterns can be implemented with functional electrical stimulation. The study is motivated by the fact that the existing crutch-assisted gait realized by the electrical stimulation is slow and energy inefficient. Gait patterns that would improve the walking are identified. The main characteristic of the patterns is that some of their states are not statically stable. During such states, the subject is supported by only a leg and a crutch. It is demonstrated that if the forward motion is provided by the stimulation of the plantar flexors the trajectory of the center of the body can closely follow the trajectory that is observed during walking of healthy subjects. We argue that the resulting gait is smooth and energy efficient. In addition, the unstable states make the walking faster.

Improved walking of completely paralyzed paraplegic subjects assisted by multichannel functional electrical stimulation (FES) and crutches is proposed. In the resulting quadrupedal gait the center of body (COB) is both actively and passively transferred in the direction of progression. Active transfer of the COB is accomplished by electrical stimulation of ankle plantarflexors of the trailing leg. Passive displacement of the COB occurs during the unstable state when the paraplegic person is only supported by a single foot and the contralateral crutch. Comparison of the time parameters measured during human crawling on knees and arms with the crutch assisted walking is presented. Results of kinematic modeling of the present and the improved FES and crutch assisted walking are displayed in the form of supporting polygons with the trajectory of the COB projected to the ground.

Walking in completely paralyzed paraplegic persons can be realized by passive mechanical bracing or multichannel functional electrical stimulation (FES) of paralyzed lower extremities. In both cases the equilibrium has to be provided by the use of crutches. Restored walking in completely paralyzed persons can be, therefore, treated as four-legged locomotion, closely resembling the walking patterns encountered in walking machines. In this way the gait pattern can be described as a sequence of the states displaying the contacts of both feet and both crutches with the ground. Improved four-point gait modalities are proposed by introducing unstable states into the walking sequence. The unstable states are defined as passive gait phases where the body is only supported in two contact points and where the center of body is gravity and inertia driven in the direction of progression. Kinematic measurements of the unstable state were performed in paraplegic subject by assessing the horizontal displacement of the center of body (COB) in the plane of progression.>

Robotic applications often involve manipulation of objects where position and orientation are not perfectly known. Pushing an object for instance by a fence, can be employed to accurately align parts, reducing uncertainty to only one degree of freedom. In this paper a pushing task involving two fingers that completely constrains an object in a plane is proposed. The stability of orientation and position of an object being pushed is discussed. The solution obtained is unique despite the fact that the distribution of forces supporting the object cannot, in general, be known. The proposed task of pushing is simple although some preliminary information about the initial position and orientation of an object is required. An approach to avoid the ambiguity in orientation, owing to the effect of friction between the object and the pusher, by introducing up and down movement of the pusher is also presented.>