This paper presents a electromyography (EMG) control for a hand exoskeleton. The device was developed with focus on support of the rehabilitation process after hand injuries or strokes. As the device is designed for the later use on patients, which have limited hand mobility, fast undesired movements have to be averted. Safety precautions in the hardware and software design of the system must be taken to ensure this. The construction allows controlling the motion of finger joints. However, due to friction in gears and mechanical construction it is not possible to move finger joints within the construction without help of actuators. Therefore force sensors are integrated into the construction to measure force exchanged between human and exoskeleton. These allow the human to control the movements of the hand exoskeleton which is useful to teach new trajectories, for muscle training, or for diagnostic purposes. The control method using electromyography (EMG) sensor presented in this paper uses the EMG sensor values to generate a trajectory, which is executed by a position control loop based on sliding mode control.

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Hand injuries are a frequent problem. The great amount of hand injuries is not only a problem for the affected people but economic consequences follow because rehabilitation takes a long time. To improve therapy results and reduce cost of rehabilitation a handexoskeleton was developed. For research on control algorithms and rehabilitation programs a prototype supporting all four degrees of freedom of one finger was built (s. Fig. 1). In view of the fact that a lot of hand injuries affect only one finger, this prototype could already be functional in physical therapy. A robust sliding mode controller was proposed for motion control of the handexoskeleton. The performance of the controller was evaluated for step response. In a second experiment varied forces where applied during the sensor was set to hold a constant position. Finally the controller was set to follow a complete trajectory.

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Cerebral palsy is an occurrence in which the nerves and muscles if the body may function properly, but there is damage to the brain that causes it to transmit incorrect electri-cal impulses to the muscles including both too many and too few signals. Without the correct cohesive electrical impulses to balance the opposing muscles of a joint, normal everyday tasks that most of us take for granted become very difficult to learn and perform. As exoskeletons become more advanced and practical, their applications have a lot of room for growth. Cerebral Palsy is one portion of the medical field that can benefit from the development of exoskeletons. As demonstrated with modern rehabilitation techniques, the application of an exoskeleton has the possibility of making the learning process and performance of many tasks easier and faster for both the patient as well as the doctor working with them. However, in order to appropriately apply the technology to the need, many changes in both the controls and the actual physical design of current devices need to be addressed. An exoskeleton for the purpose of helping cerebral palsy patients learn to walk is not limited to one specific form depending on the complexity of the tasks it is desired to assist with. However, there are a couple needs of this type of exoskeleton that are absolutely necessary. The size of the exoskeleton must be designed around the size of a child and not an adult. If the individual is learning to walk from the very beginning, the controls of the device will need to initially be able to take complete control over the individual’s limbs to exercise the motions of walking. With the nature of an exoskeleton controlling the limbs of a person instead of simply assisting with current movements, the physical attachments of the exoskeleton must be improved from current designs in order to make movements of the exoskeleton and the body more parallel. Other features such as different muscle sensing techniques may also improve performance, but are not required. An exoskeleton that can help cerebral palsy patients learn to walk can also be applied to many other rehabilitation needs.

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Background: It has been shown that intense training can significantly improve post-stroke upperlimb functionality. However, opportunities for stroke survivors to practice rehabilitation exercises can be limited because of the finite availability of therapists and equipment. This paper presents a haptic-enabled exercise platform intended to assist therapists and mo-derate-level stroke survivors perform upper-limb reaching motion therapy. This work extends on existing knowledge by presenting: 1) an anthropometrically-inspired design that maximizes elbow and shoulder range of motions during exercise; 2) an unobtrusive upper body postural sensing system; and 3) a vibratory elbow stimulation device to encourage muscle movement. Methods: A multi-disciplinary team of professionals were involved in identifying the rehabilitation needs of stroke survivors incorporating these into a proto-type device. The prototype system consisted of an exercise device, postural sensors, and a elbow stimula- tion to encourage the reaching movement. Eight experienced physical and occupational therapists partici-pated in a pilot study exploring the usability of the prototype. Each therapist attended two sessions of one hour each to test and evaluate the proposed system. Feedback about the device was obtained through an administered questionnaire and combined with quantitative data. Results: Seven of the nine questions regar-ding the haptic exercise device scored higher than 3.0 (somewhat good) out of 4.0 (good). The postural sensors detected 93 of 96 (97%) therapistsimulated abnormal postures and correctly ignored 90 of 96 (94%) of normal postures. The elbow stimulation device had a score lower than 2.5 (neutral) for all as-pects that were surveyed, however the therapists felt the rehabilitation system was sufficient for use without the elbow stimulation device. Conclusion: All eight therapists felt the exercise platform could be a good tool to use in upperlimb rehabilitation as the prototype was considered to be generally well de-signed and capable of delivering reaching task therapy. The next stage of this project is to proceed to clinical trials with stroke patients.

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Robotic lower limb exoskeletons that can alter joint mechanical power output are novel tools for studying the relationship between the mechanics and energetics of human locomotion. We built pneumatically powered ankle exoskeletons controlled by the user’s own soleus electromyography (i.e. proportional myoelectric control) to determine whether mechanical assistance at the ankle joint could reduce the metabolic cost of level, steady-speed human walking. We hypothesized that subjects would reduce their net metabolic power in proportion to the average positive mechanical power delivered by the bilateral ankle exoskeletons. Nine healthy individuals completed three 30 min sessions walking at 1.25 m s–1 while wearing the exoskeletons. Over the three sessions, subjects’ net metabolic energy expenditure during powered walking progressed from +7% to –10% of that during unpowered walking. With practice, subjects significantly reduced soleus muscle activity (by ∼28% root mean square EMG, P<0.0001) and negative exoskeleton mechanical power (–0.09 W kg–1 at the beginning of session 1 and –0.03 W kg–1 at the end of session 3; P=0.005). Ankle joint kinematics returned to similar patterns to those observed during unpowered walking. At the end of the third session, the powered exoskeletons delivered ∼63% of the average ankle joint positive mechanical power and ∼22% of the total positive mechanical power generated by all of the joints summed (ankle, knee and hip) during unpowered walking. Decreases in total joint positive mechanical power due to powered ankle assistance (∼22%) were not proportional to reductions in net metabolic power (∼10%). The `apparent efficiency’ of the ankle joint muscle–tendon system during human walking (∼0.61) was much greater than reported values of the `muscular efficiency’ of positive mechanical work for human muscle (∼0.10–0.34). High ankle joint `apparent efficiency’ suggests that recoiling Achilles’ tendon contributes a significant amount of ankle joint positive power during the push-off phase of walking in humans.

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