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Upper Limb Exoskeletons

A similar approach to identifying LLEs was used to identify ULE systems. We adhered to our definition of ULE for manipulation with potential for use as an AT and included only systems that have been studied during use by people with a disability. A similar search strategy was employed as a recent systematic review (Maciejasz et al. 2014) to compile this list of ULE systems; the notable difference was the necessity for systems to be demonstrated for use with ADLs rather than for rehabilitation. The search revealed only one commercially available ULE, but also found were some research-only systems that were developed around the world. All these required multiple actuated joints to be included, consistent with our exoskeleton definition as a “multi-joint orthosis that uses an external power source to move at least two joints” for use in daily life scenarios. Thus, several systems with only a single actuator were not included; also not included were systems incorporating an upper limb orthosis with movements initiated by FES alone rather than incorporating external actuators. Several systems with demonstrated use only by able-bodied study participants were also not included. Table 6.3 lists specific details of each system. Maciejasz et al. (2014) included a list of systems that did not meet our criteria for inclusion here.

The MyoPro Motion-G, a portable elbow-wrist-hand orthosis, was recently launched by the medical device company Myomo, Incorporated, of Cambridge, Massachusetts (http://www.myomo.com/). The MyoPro Motion-G is the third generation of a previously developed arm (elbow) orthosis called Myomo e100 (Stein 2009). Myomo e100 was developed and FDA approved in 2007 as a class II medical device, with class II devices subject to special controls with a higher level of assurance of user safety than class I devices. The MyoPro Motion-G (Table 6.2) provides flexion/ extension actuation at the elbow joint and grasping capabilities to perform ADL, including feeding, reaching, and lifting. User intention is detected by the use of EMG signals recorded from biceps, triceps, forearm flexor, and forearm extensor muscle group activations. Because the device uses residual muscle activity, it cannot be used by those with complete paralysis. For any individual user, the level of assistance provided by the orthosis is set based on the user’s individual muscle signals as measured by a certified orthotist. Several training sessions are necessary to acquire a base level of proficiency. The target population for this orthosis is people with upper limb disorders, including neuromuscular conditions such as BPI, traumatic brain injury, SCI, MS, ALS, and stroke. The company claims that the MyoPro Motion-G can improve a person’s independence in performing ADLs and also emphasizes that, unlike most of the LLEs, this device is not intended as a rehabilitation device. Rather, its objective design use is as an AT (Figure 6.2).

MUNDUS (Multimodal Neuroprosthesis for Daily Upper limb Support) was a focused ULE research project that ended in 2013 and was funded by the European Commission. MUNDUS was developed as an AT research platform to perform reaching and grasping of objects and positioning the arm in space (Pedrocchi et al. 2013). The exoskeleton is a lightweight, antigravity orthosis that provides 2 degrees of freedom (DOF) at the shoulder joint (shoulder elevation in the sagittal plane and shoulder rotation in the horizontal elevation plane) and 1 DOF at the elbow joint. If there is no residual hand function, an actuated hand orthosis is included. Electromagnetic brakes are implemented in the mechanical design of the exoskeleton to provide weight support during use. Neuromuscular electrical stimulation (NMES) is applied to the upper arm muscles to control the motion of the upper extremity; thus, it is debatable whether this

TABLE 6.3 ULE Device Characteristics and Technology Readiness Level Score

Device

Name

Joint Type

Supported

Movements

Target Users

Type of Control

Commercially

Available

TRL

MyoPro®

Motion-G

Elbow flexion/extension Hand grasping function

Reaching

Grasping

Brachial plexus injury Traumatic brain injury SCI, ALS, stroke Multiple sclerosis

Intention detection through residual EMG activity

Yes

8

MUNDUS

Shoulder elevation/rotation Elbow flexion/extension Actuated hand grasp (optional)

Reaching

Grasping

SCI, ALS Friedreich ataxia Multiple sclerosis

Joystick control by opposite hand

No

6

WOTAS

Elbow flexion/extension Forearm pronation/supination Wrist flexion/extension

Tremor

suppression

Any neurological disorders that cause tremor

Real-time tremor suppression algorithm

No

6

The MyoPro® Motion-G upper limb exoskeleton, intended for use as an assistive technology. (Photograph courtesy of Myomo, Incorporated.)

Figure 6.2 The MyoPro® Motion-G upper limb exoskeleton, intended for use as an assistive technology. (Photograph courtesy of Myomo, Incorporated.)

device should be included in this chapter because only the hand module has externally actuated control (i.e., a single joint of external actuation and another 2 DOF controlled by NMES).

According to the severity of the impairment, three different control strategies were implemented in the first MUNDUS prototype. The first mode used EMG sensors and residual activation of the user’s muscles to execute a certain task. The second mode was designed for those with lack of arm and hand muscle activity and detects user intention with an eyetracking system. In the ultimate progression of some diseases, the user may have no gaze control; in this case, the third control mode utilizes an EEG-based BCI. Functionality of the device is restricted to a set of predefined tasks when the second or third control strategy is deployed. The MUNDUS system was a research prototype, but was stated to be currently under commercial development (Pedrocchi et al. 2013).

WOTAS (Wearable Orthosis for Tremor Assessment and Suppression) is a portable, powered ULE that aims to suppress tremors. Three DOF are considered in the mechanical structure of the device, corresponding to elbow flexion/extension, forearm pronation/supination, and wrist flexion/ extension. Both kinematic and kinetic sensors are used to measure the state of the joint angles, angular velocities, as well as interaction forces between limb and orthosis. Signals are then used to develop a control strategy to be delivered to the onboard motors. This results in the application of an equal and opposite force that cancels out tremulous movement (Rocon et al. 2007).

A brief introduction of other ULE devices that were designed and tested, but did not meet our inclusion criteria with published testing results when used by a person with a disability, follows. MULOS

(Motorized Upper-Limb Orthotic System) is a 5-DOF, electrically powered, wheelchair-mounted device (Johnson et al. 2001). The design provides 3 DOF at the shoulder, 1 DOF at the elbow, and 1 DOF at the forearm to perform pronation/supination. The device can be directly worn by the user and is controlled by a 5-DOF joystick that is operated by the intact side of the user’s body. The target population for the use of this device is considered to be the elderly and people in general with upper limb disabilities.

The upper limb-type HAL (HAL-UL) is a wearable robotic suit that provides meal assistance, developed by the same Japanese group who developed the LLE HAL. The design has 3 DOF in the shoulder joint, 1 DOF in the elbow joint, and 3 DOF in the wrist joint. Although the mechanical structure of the system seems to have the potential to provide different manipulation tasks, the only published study regarding the use of this exoskeleton suit addressed performing a meal assistance task (Kawamoto et al. 2011).

The 7 degrees of freedom upper limb motion assist exoskeleton robot (SUEFUL-7) is an upper limb exoskeleton robot that is controlled by residual EMG signals. The SUEFUL-7 assists the motions of shoulder vertical and horizontal flexion/extension, shoulder internal/external rotation, elbow flexion/extension, forearm supination/pronation, wrist flexion/ extension, and wrist radial/ulnar deviation. Several kinematic and kinetic sensors are used to evaluate the real-time postural configuration of the user as well as forces and torques that are generated between the arm and the orthosis. An experimental study showed that the EMG levels were reduced when the device was used, thus indicating that the device provided external assistance during movements (Gopura, Kiguchi, and Yi 2009).

 
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