Exoskeletons for Human Performance Augmentation 33.2 Upper-Extremity Exoskeleton 775 ing muscle strength.In addition to electromyography tor coupling the upper and the lower portions of a knee (EMG)signals,the device further includes potentiome-brace.The control of this powered knee brace requires ters for measuring the joint angles,force sensors for the ground reaction force measured by two load cells. measuring the ground reaction forces and a gyroscope The system uses a positive-feedback force controller to and accelerometer for measuring the torso angle.Each create an appropriate force for the actuator. leg of HAL powers the flexion/extension motion at the Kong et al.developed a full lower-limb exoskeleton hip and knee in the sagittal plane through the use of system that works with a powered walker [33.15].The DC motors integrated with harmonic drives.The ankle walker houses the electric actuators,the controller,and includes passive degrees of freedom. the batteries,reducing the weight of the exoskeleton Yamamoto et al.[33.10,11]have created an exoskel- system.A transmission system transmits power to the eton system for assisting nurses during patient handling. wearer's joints from the actuators in the walker.The The lower limbs include pneumatic actuators for the exoskeleton is powered at the hips and knees in sagittal flexion/extension of the hips and knees in the sagittal plane.The input to drive the system is a set of pressure plane.Air pumps are mounted directly onto each actua-sensor that measure the force applied by the quadriceps tor to provide pneumatic power.User input is determined muscle on the knee. via force sensing resistors coupled to the wearer's skin. Agrawal et al.have conducted research projects on The measurement from force sensing resistor (FSR)statically balanced leg orthoses that allow for less effort and other information such as joint angles are used to during swing [33.16].In the passive version,the device determine the required input torques for various joints.uses springs in order to cancel the gravity force associ- Pratt et al.developed a powered knee brace for ated with the device links and the person leg.Through adding power at the knee to assist in squatting [33.12]. experiments the authors showed that the device reduced The device is powered by a linear series-elastic actua- the required torque by the wearer substantially. 33.2 Upper-Extremity Exoskeleton In the mid-1980s,researchers at Berkeley initiated sev- movements accordingly,but the force he/she feels is eral research projects on upper-extremity exoskeleton much smaller than what he/she would feel without the systems,billed as human extenders [33.17-23].The device.In another example,suppose the worker uses main function of an upper-extremity exoskeleton is the device to maneuver a large,rigid,and bulky ob- human power augmentation for the manipulation of ject,such as an exhaust pipe.The device will convey heavy and bulky objects.Since upper-extremity ex- the force to the worker as if it was a light,single- oskeletons are mostly used for factory floors,warehouse, point mass.This limits the cross-coupled and centrifugal and distribution centers,they are hung from overhead forces that increase the difficulty of maneuvering a rigid cranes.As can be seen in later sections,lower-extremity body and can sometimes produce injurious forces on exoskeletons focus on supporting and carrying heavy the wrist.In a third example,suppose a worker uses payloads on the operator's back(like a backpack)during the device to handle a powered torque wrench.The de- long-distance locomotion.Upper-extremity exoskele-vice will decrease and filter the forces transferred from tons,which are also known as assist devices or human the wrench to the worker's arm so the worker feels the power extenders,can simulate forces on a worker's low-frequency components of the wrench's vibratory arms and torso.These forces differ from,and are usu-forces instead of the high-frequency components that ally much smaller than the forces needed to maneuver produce fatigue [33.24].These assist devices not only a load.When a worker uses an upper-extremity exoskel- filter out unwanted forces on a worker.but can also be eton to move a load,the device bears the bulk of the programmed to follow a particular trajectory regardless weight by itself,while transferring to the user as a nat-of the exact direction in which the worker attempts to ural feedback a scaled-down value of the load's actual manipulate the device.For example,suppose an auto- Part weight.For example,for every 20kg of weight from an assembly worker is using an assist device to move a seat object,a worker might support only 2 kg while the de-to its final destination inside a car.The assist device can 出 vice supports the remaining 18 kg.In this fashion,the bring the seat to its final destination,moving it along worker can still sense the load's weight and judge his/her a preprogrammed path with a speed that is proportionalExoskeletons for Human Performance Augmentation 33.2 Upper-Extremity Exoskeleton 775 ing muscle strength. In addition to electromyography (EMG) signals, the device further includes potentiome￾ters for measuring the joint angles, force sensors for measuring the ground reaction forces and a gyroscope and accelerometer for measuring the torso angle. Each leg of HAL powers the flexion/extension motion at the hip and knee in the sagittal plane through the use of DC motors integrated with harmonic drives. The ankle includes passive degrees of freedom. Yamamoto et al. [33.10,11] have created an exoskel￾eton system for assisting nurses during patient handling. The lower limbs include pneumatic actuators for the flexion/extension of the hips and knees in the sagittal plane. Air pumps are mounted directly onto each actua￾tor to provide pneumatic power. User input is determined via force sensing resistors coupled to the wearer’s skin. The measurement from force sensing resistor (FSR) and other information such as joint angles are used to determine the required input torques for various joints. Pratt et al. developed a powered knee brace for adding power at the knee to assist in squatting [33.12]. The device is powered by a linear series-elastic actua￾tor coupling the upper and the lower portions of a knee brace. The control of this powered knee brace requires the ground reaction force measured by two load cells. The system uses a positive-feedback force controller to create an appropriate force for the actuator. Kong et al. developed a full lower-limb exoskeleton system that works with a powered walker [33.15]. The walker houses the electric actuators, the controller, and the batteries, reducing the weight of the exoskeleton system. A transmission system transmits power to the wearer’s joints from the actuators in the walker. The exoskeleton is powered at the hips and knees in sagittal plane. The input to drive the system is a set of pressure sensor that measure the force applied by the quadriceps muscle on the knee. Agrawal et al. have conducted research projects on statically balanced leg orthoses that allow for less effort during swing [33.16]. In the passive version, the device uses springs in order to cancel the gravity force associ￾ated with the device links and the person leg. Through experiments the authors showed that the device reduced the required torque by the wearer substantially. 33.2 Upper-Extremity Exoskeleton In the mid-1980s, researchers at Berkeley initiated sev￾eral research projects on upper-extremity exoskeleton systems, billed as human extenders [33.17–23]. The main function of an upper-extremity exoskeleton is human power augmentation for the manipulation of heavy and bulky objects. Since upper-extremity ex￾oskeletons are mostly used for factory floors, warehouse, and distribution centers, they are hung from overhead cranes. As can be seen in later sections, lower-extremity exoskeletons focus on supporting and carrying heavy payloads on the operator’s back (like a backpack) during long-distance locomotion. Upper-extremity exoskele￾tons, which are also known as assist devices or human power extenders, can simulate forces on a worker’s arms and torso. These forces differ from, and are usu￾ally much smaller than the forces needed to maneuver a load. When a worker uses an upper-extremity exoskel￾eton to move a load, the device bears the bulk of the weight by itself, while transferring to the user as a nat￾ural feedback a scaled-down value of the load’s actual weight. For example, for every 20 kg of weight from an object, a worker might support only 2 kg while the de￾vice supports the remaining 18 kg. In this fashion, the worker can still sense the load’s weight and judge his/her movements accordingly, but the force he/she feels is much smaller than what he/she would feel without the device. In another example, suppose the worker uses the device to maneuver a large, rigid, and bulky ob￾ject, such as an exhaust pipe. The device will convey the force to the worker as if it was a light, single￾point mass. This limits the cross-coupled and centrifugal forces that increase the difficulty of maneuvering a rigid body and can sometimes produce injurious forces on the wrist. In a third example, suppose a worker uses the device to handle a powered torque wrench. The de￾vice will decrease and filter the forces transferred from the wrench to the worker’s arm so the worker feels the low-frequency components of the wrench’s vibratory forces instead of the high-frequency components that produce fatigue [33.24]. These assist devices not only filter out unwanted forces on a worker, but can also be programmed to follow a particular trajectory regardless of the exact direction in which the worker attempts to manipulate the device. For example, suppose an auto￾assembly worker is using an assist device to move a seat to its final destination inside a car. The assist device can bring the seat to its final destination, moving it along a preprogrammed path with a speed that is proportional Part D 33.2