Virtual Reality (VR) provides a unique medium suited to the achievement of several requirements for effective rehabilitation intervention. Specifically, thera-py can be provided within a functional, purposeful and motivating context. Many VR applications present op-portunities for individuals to participate in experiences, which are engaging and rewarding. In addition to the value of the rehabilitation experience for the user, both therapists and users benefit from the abi-lity to readily grade and document the therapeutic intervention using various systems. In VR, advanced technologies are used to produce simulated, interactive and multi-dimensional environments. Visual inter-faces including desktop monitors and head-mounted displays (HMDs), haptic interfaces, and real-time motion tracking devices are used to create environments allowing users to interact with images and virtual ob-jects in real-time through multiple sensory modalities. Opportunities for object manipulation and body mo-vement through virtual space provide frameworks that, in varying degrees, are perceived as comparable to similar opportunities in the real world. This paper reviews current work on motor rehabilitation using vir-tual environments and virtual reality and where possible, compares outcomes with those achieved in real-world applications.

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This paper describes the mechanical and electrical design of a compact high fidelity desktop haptic interface that provides three-degree-of-freedom point-force interaction through a handheld pen-like stylus. The complete haptic device combines a spatial linkage, actuation, power amplification, and control electronics in a standalone package with a footprint similar to that of a notebook computer (33cm x 25cm x 10cm). The procedure used to design the statically balanced spatial linkage is explained and both an inexpensive lightweight plastic version and a high stiffness, high strength, aluminum and stainless steel version are presented. The theory and implementation of sinusoidal encoder interpolation and sinusoidal servo-motor commutation used to achieve high-fidelity haptic simulation is covered for two versions of electronic control hardware: custom hardware based on a digital signal processor (DSP) and an off-the-shelf design based on an embedded PC.

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A high-quality haptic interface is typically characterized by low apparent inertia and damping, high structural stiffness, minimal backlash and absence of mechanical singu-larities in the workspace. In addition to these specifications, exoskeleton haptic interface design involves consideration of additional parameters and constraints including space and weight limitations, workspace requirements and the kinematic constraints placed on the device by the human arm. In this context, we present the design of a five degree-of-freedom haptic arm exoskeleton for training and rehabi-litation in virtual environments. The design of the device, including actuator and sensor selection, is discussed. Limitations of the device that result from the above selections are also presented. The device is capable of providing kinesthetic feedback to the joints of the lower arm and wrist of the operator, and will be used in future work for robot-assisted rehabilitation and training.

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A networked control system (NCS) is a control architecture where sensors, actuators and controllers are distributed and interconnected. It is advantageous in terms of interoperability, expandability, installation, volume of wiring, maintenance, and cost-effectiveness. Many distributed network systems of various topologies and network types have been developed, but NCS systems tend to suffer from such issues as nondeterminism, long network delays, large overheads and unfairness. This paper presents the ring-based protocol, called the ExoNet, and its network architecture which are built to achieve better performance as a distributed networked system. A Cypress transceiver CY7C924ADX is applied to the network as a communication unit. The protocol is based on the transceiver and developed to achieve fast communication and allowable latency for controls with high control loop frequency. Compared with other standard network types such as Ethernet, ControlNet or DeviceNet, the network is characterized by its ring-based architecture, simple message and packet formats, one-shot distribution of control data and collection of sensor data, multi-node transmission, echo of a message, and other features. The network also guarantees determinism, collision-free transmission, relatively small overhead, fairness between nodes and flexibility in configuration. Its analysis and comparison with these network types are also provided and its application on the Berkeley Lower-Extremity Exoskeleton (BLEEX) is described.

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To restore dexterity to paralyzed hands, we have designed and constructed a lightweight, low-profile orthotic exoskeleton controlled by the user’s residual electromyography (EMG) signals. In this paper, we compared several simple strategies to control the orthotic device for a quadriplegic (C5/C6) subject. When contralateral arm control was employed, we found that a simple on/off strategy allowed for faster interaction with objects, while variable control provided more controlled interactions, especially with deformable objects. Furthermore, we designed a control strategy that allowed for a natural reaching and pinching sequence without the use of the contralateral arm. We validated that the EMG signal from the ipsilateral biceps could be used to develop an extremely reliable natural reaching and pinching algorithm. This evaluation showed that different control strategies may be appropriate for different situations, and further investigation on the natural algorithm is crucial.

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