Exoskeletons and Soft Robotics
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- Soft wearable robots that use
innovative textiles to provide a more conformal, unobtrusive and compliant
means to interface to the human body. These robots will augment the
capabilities of healthy individuals (e.g. improved walking efficiency) in
addition to assisting those with muscle weakness or patients who suffer from
physical or neurological disorders.
Product Portfolio
Harvard Biodesign Lab
Soft Exosuits
- We are developing next generation soft wearable robots
that use innovative textiles to provide a more conformal, unobtrusive and
compliant means to interface to the human body. These robots will augment
the capabilities of healthy individuals (e.g. improved walking efficiency)
in addition to assisting those with muscle weakness or patients who suffer
from physical or neurological disorders. As compared to a traditional
exoskeleton, these systems have several advantages: the wearer's joints are
unconstrained by external rigid structures, and the worn part of the suit is
extremely light. These properties minimize the suit's unintentional
interference with the body's natural biomechanics and allow for more
synergistic interaction with the wearer.
Structured functional textiles
- We are creating innovative textiles that are inspired by
an understanding of human biomechanics and anatomy. These wearable garments
provide means to transmit assistive torques to a wearer’s joints without the
use of rigid external structures. In order to obtain high-performance soft
exosuits, some considerations should be taken into account in the design
process. Exosuits should attach to the body securely and comfortably, and
transmit forces over the body through beneficial paths such that
biologically-appropriate moments are created at the joints. In addition,
these garments can be designed to passively (with no active power) generate
assistive forces due to the natural movement of the wear for particular
tasks. A key feature of exosuits is that if the actuated segments are
extended, the suit length can increase so that the entire suit is slack, at
which point wearing an exosuit feels like wearing a pair of pants and does
not restrict the wearer whatsoever.
Lightweight and efficient actuation
- In order to provide active assistance through the soft
interface, we are developing a number of actuation platforms that can apply
controlled forces to the wearer by attaching at anchoring points in the
wearable garment. We are developing lightweight and fully portable systems
and a key feature of our approach is that we minimize the distal mass that
is attached to the wearer through more proximally mounted actuation systems
and flexible transmissions that transmit power to the joints. While most of
our recent work is on cable-driven electromechanical approaches, we have
also pursued pneumatic based approaches. This early work with McKibbon
actuators in 2013 was the first demonstration that a soft exosuit can have a
positive effect on mobility.
Wearable sensors
- New sensor systems that are easy to integrate with
textiles and soft components are required in order to properly control and
evaluate soft exosuits. Rigid exoskeletons usually include sensors such as
encoders or potentiometers in robotic joints that accurately track joint
angles, but these technologies are not compatible with soft structures. Our
approach is to design new sensors to measure human kinematics and suit-human
interaction forces that are robust, compliant, cost effective, and offer
easy integration into wearable garments. In addition, we use other off the
shelf sensor technologies (e.g. gyro, pressure sensor, IMU) that can be used
to detect key events in the gait cycle. These wearable sensors can be used
as part of the control strategy for the wearable robot or alternatively to
monitor and record the movement of the wearer (when wearing the exosuit or
as a standalone sensor suit) for tracking changes over time or determining
what activities they are performing (e.g. walking vs running).
Intuitive and robust control
- We are also developing rapidly reconfigurable
multi-actuator systems that provide more flexibility for lab-based studies.
Such an approach allows us to rapidly explore the basic science around
human-machine interaction with such systems that can then be used to guide
the design of our portable systems. A robust, intuitive and adaptive
human-machine interface is a necessary component for a wearable robot to
interact synergistically with the wearer. Our focus is to provide assistance
in a manner that does not disrupt the natural, passive dynamics that make
walking or running so efficient. To achieve this, we develop approaches to
non-invasively estimate the intent so that any actuation applied assists
that from the appropriate biological muscles. A key feature of our approach
is to leverage integrated sensors that monitor the wearer interaction with
the compliant textile that interfaces to the body as well as other sensors
that detect key moment during the gait cycle.
Experimental biomechanics
- Our motion capture lab utilizes a Vicon T-series 9-camera
system for motion capture, together with a Bertec fully instrumented
split-belt treadmill to measure GRFs. By comparing the average profile and
range of motion of each joint in the three conditions, we can identify how
the soft exosuit itself impacts gait and how the assistance applied by the
exosuit changes kinematics. Our hypothesis is that it is desirable that such
changes are minimal and in any case not disruptive to natural gait. We study
to what extent the active exosuit is assisting the human by analyzing gait
dynamics and kinetics (joint moments, power, force delivered by the exosuit).
Inverse dynamics is an effective way to determine to what degree the exosuit
is augmenting the body function at a joint level. The comparison of joint
moments and suit assistive forces allows us to monitor the degree of
synchronicity between the user and the robot. Surface electromyography (sEMG)
can be used to selectively monitor muscular activity focusing on the muscle
groups that are most relevant for the task under consideration. Comparing
the ensemble average profiles of sEMG activity between the unpowered, active
and no suit conditions allows us to determine effects on the maximum force
being delivered by each muscle (peak sEMG activation) and on the energy cost
of each muscle activation (integral sEMG). We use the metabolic cost of
walking as a global physiological measurement to determine to what extent
the suit is assisting the wearer and if assistance offsets the weight of the
device.
Translational applications
- In addition to our work on basic research and system
development, we are highly interested in pursuing applications of our soft
wearable robots. Through our DARPA funded work, we are interested in
developing exosuits that can assist soldiers walking while carrying heavy
loads. Our belief is we can create passive and active systems that offload
the high forces in the muscles and tendons in the leg – thus reducing the
risk of injury and increasing the walking efficiency of the wearer. Another
translational focus of our group is on gait assistance for medical
applications. We foresee soft exosuits being able to restore mobility on
patients with muscle weakness (e.g. elderly) or who suffer from a
neurological disease such as a Stroke. Beyond our active systems, we
envision translational potential in the area of sports and recreation where
fully passive soft suits with structured functional textiles can provide
small amounts of assistance during walking, hiking, running and other
activities.
Soft Robotics
Multi-material fluidic actuators
- Soft fluidic actuators consisting of elastomeric matrices
with embedded flexible materials (e.g. cloth, paper, fiber, particles) are
of particular interest to the robotics community because they are
lightweight, affordable and easily customized to a given application. These
actuators can be rapidly fabricated in a multi-step molding process and can
achieve combinations of contraction, extension, bending and twisting with
simple control inputs such as pressurized fluid. In our approach is to use
new design concepts, fabrication approaches and soft materials to improve
the performance of these actuators compared to existing designs. In
particular, we use motivating applications (e.g. heart assist devices, soft
robotic gloves) to define motion and force profile requirements. We can then
embed mechanical intelligence into these soft actuators to achieve these
performance requirements with simple control inputs.
Modeling of soft actuators
- Characterizing and predicting the behavior of soft
multi-material actuators is challenging due to the nonlinear nature of both
the hyper-elastic material and the large bending motions they produce. We
are working to comprehensively describe the principle of operation of these
actuators through analytical, numerical and experimental approaches and
characterize their outputs (motion and force) as a function of input
pressure as well as geometrical and material parameters. Both models and
experiments offer insight into the actuator behavior and the design
parameters that affect it. We envision this work will lead to improved
predictive models that will enable us to rapidly converge on new and
innovative applications of these soft actuators.
Sensing and control
- In order to control soft actuators, we need means of
monitoring their kinematics, interaction forces with objects in the
environment and internal pressure. We accomplish this through the use of
fully soft sensors, developed with collaborators, and miniature or flexible
sensors that can be incorporated into the actuator design during the
manufacturing process. For power and control, we use off the shelf
components such as electronic valves, pumps, regulators, sensors, and
control boards etc. to rapidly modulate the pressure inside the chambers of
the actuators using feedback control of pressure, motion and force. In
addition, we can use the analytical models we develop to estimate state
variables that may be difficult to measure directly.
Translational applications
- There are approximately four million chronic stroke
survivors with hemiparesis in the US today and another six million in
developed countries globally. In addition, there are millions of other
individuals suffering from similar conditions. For the majority of these
cases, loss of hand motor ability is observed, and whether partial or total,
this can greatly inhibit activities of daily living (ADL) and can
considerably reduce one’s quality of life. To address these challenges, we
are developing a modular, safe, portable, consumable, at-home hand
rehabilitation and assistive device that aims to improve patient outcomes by
significantly increasing the quantity (i.e. time) and quality of therapy at
a reduced cost while also improving independence of users with chronic hand
disabilities by enabling them to perform activities of daily living.
In the United States, the lifetime risk of developing heart failure is
roughly 20%. The current clinical standard treatment is implantation of a
ventricular assist device that contacts the patient’s blood and is
associated with thromboembolic events, hemolysis, immune reactions and
infections. We are applying the field of soft robotics to develop a benchtop
cardiac simulator and a Direct Cardiac Compression (DCC) device employing
soft actuators in an elastomeric matrix. DCC is a non-blood contacting
method of cardiac assistance for treating heart failure involving
implantation of a device that surrounds the heart and contracts in phase
with the native heartbeat to provide direct mechanical assistance during the
ejection phase (systole) and the relaxation phase (diastole) of the cardiac
cycle.
Université Libre de Bruxelles (ULB)
-
Portable Arm Exoskeleton
- In many teleoperated or virtual activities with force
feedback, the use of a fully portable haptic device would increase the
easiness and performances of the command task, compared to devices linked to
the ground or a table. Applications range from robotic arm teleoperation in
severe environments (space, nuclear reactors, deep waters…). to applications
in virtual reality either in the domain of virtual training in large volumes
(such as virtual assembly) by means of immersion caves or head mounted
displays or in the domain of stroke patients rehabilitation. As the
operator does not have to be linked to a fixed base, or in environments with
obstacles and as a multi-DOF portable device allows force feedback on
several contact points, the operator is more immersed in the environment
during the manipulation.
The Sensoric Arm Master (SAM) has been designed as a wearable haptic
interface with a serial kinematics, isomorphic to the human arm. SAM
contains 7 actuated DOF corresponding to the joints of the human arm
(shoulder, elbow and wrist flexion/extension, shoulder and wrist
adduction/abduction, arm and forearm pronation/supination) and 6 sliders
allowing morphological adaptation between active joints and human
articulations. That corresponds to a good compromise between operator
immersion capabilities (maximised workspace and no singularity) and
mechanical complexity. Each joint of the exoskeleton has a similar
conception with a local actuator, a position and torque sensor, allowing
several kinds of control strategies (impedance, admittance control). The
actuation has been selected with a compact system composed of a brushed DC
motor, a capstan and gearbox.
SAM exoskeleton
Sam joint design
University of California, Santa Cruz
Wearable Robotics - Exoskeletons
- The exoskeleton robot is worn by the human operator as
an orthotic device. Its joints and links correspond to those of the human
body. The same system operated in different modes can be used for three
fundamental applications: a human-amplifier assistive device sharing a
portion of the external load with the operator, haptic device, and automatic
physiotherapy.
The current research effort with the upper limb exoskeleton is focused on
the developing human machine interface (bioport) at the neuromuscular level
using EMG (electromyography) signals as the primary command signal to the
system. The research effort with the lower limb exoskeleton is focused on
developing a semi active system for improving the ability of the operator to
carry a payload. Exoskeleton Prototype 1 (EXO-UL1)
- The first exoskeleton mechanism consisted of a two-link,
two-joint device corresponding to the upper and the lower arm and to the
shoulder and elbow joints of the human body. The system included a weight
plate (external load) that can be attached to the tip of the exoskeleton
forearm link. The mechanism was fixed to the wall and positioned parallel to
the sagittal plane of the operator. The human/exoskeleton mechanical
interface included the upper arm bracelet, located at the upper arm link,
and a handle grasped by the operator. This two-joint mechanism was used as a
one-degree of freedom system by fixing the system shoulder joint at specific
angles in the range of 0-180 Deg. The elbow joint was free to move in an
angle range of 0-145 Deg, and included built-in mechanical constraints which
kept the exoskeleton joint angle within the average human anthropometric
boundaries. Since the human arm and the exoskeleton were mechanically linked
the movements of the forearms of both the human and the exoskeleton were
identical.
The basic purpose of the exoskeleton system as an assistance device is to
amplify the moment generated by the human muscles relative to the elbow
joint, while manipulating loads. The exoskeleton's elbow joint was powered
by a DC servo motor (ESCAP-35NT2R82) with a stall torque of 360 mNm equipped
with a planetary gearbox (ESCAP-R40) with a gear ratio of 1:193 and a
maximal output torque of 40 Nm. An optical incremental shaft encoder (HP
HEDS 5500) with 500 lines was attached to the motor shaft. Due to the
encoder location and the high gear ratio, the practical encoder's resolution
for measuring the joint angle was 0.0036 Deg. This setup incorporated a DC
motor with the highest torque-to-weight ratio that was available on the
commercial market at that time with a power consumption that could be
provided by a battery. A high energy density of the power supply and an
actuator with a high torque-to-weight ratio are two key features of the
exoskeleton system as a self contained mobile medical assistance device for
the disabled community. Limits imposed by present technology on these two
key components along with design requirements for developing a compact
system with a potential of serving as a medical assistance device for
disabled person restricted the payload to be 5 Kg. However, this biomedical
oriented design does not restrict the generality of the exoskeleton concept
or its operational algorithms. Using other actuation systems, like hydraulic
system increases the load capacity substantially.
The exoskeleton forearm was extended by a rod with a special connector for
attaching disk-type weights (external load). Two force sensors (TEDEA 1040)
were mounted at the interfaces between the exoskeleton and the tip carrying
the external load and between the exoskeleton and the human hand. The first
load cell, inserted between the rod holding the external load and the
exoskeleton forearm link, measured the actual shear force, normal to the
forearm axis, applied by the external load. The second load cell was
installed between the handle grasped by the human hand and the forearm link
of the exoskeleton. This load cell measured the shear force applied by the
operator to the handle. Multiplying the sensors' measurements by the
corresponding moment arms indicated the moments applied by the weights and
by the human hand relative the elbow joint.
Surface EMG electrodes (8 mm Ag-AgCl BIOPAC - EL208S) were attached to
the subject’s skin by adhesive disks for measuring the EMG signal of the
Biceps Brachii and Triceps Brachii medial-head muscles. The signals were
gained by EMG amplifiers (BIOPAC - EMG100A) using a gain factor in the range
of 2000-5000 (depending on the subject). The EMG signals and the load cell
signal were acquired by an A/D convector (Scientific Solution Lab Master 12
bit internal PC card) with a 1 kHz sampling rate, whereas the encoder
signals were counted by custom-made hardware. The entire data set was
recorded simultaneously and stored, for later off-line analysis and
simulation.
A special real-time software, for operating the system, was written in C and
run on a PC-based platform. The software was composed of three main modules.
The first module dealt with the hardware/software interface. It controlled
the interaction between the PC and the external motor driver and the
sensors, through a D/A and an A/D card. The second module included the
automatic code generated by the MATLAB - Simulink Real-Time toolbox. The
third module was the user interface module which allowed to set various run
time operational parameters. All the modules were compiled and linked for
generating an efficient real-time software.
Exoskeleton Prototype 2 (EXO-UL3)
- The second exoskeleton mechanism consisted of a
three-link, two-joint device corresponding to the upper and the lower arm
and to the shoulder and elbow joints of the human body. The system included
a weight plate (external load) that can be attached to the tip of the
exoskeleton forearm link. The mechanism was fixed to the wall and positioned
parallel to the sagittal plane of the operator. The human/exoskeleton
mechanical interface included the upper arm bracelet, located at the upper
arm link, and a handle grasped by the operator. This two-joint mechanism was
used as a two-degree of freedom system. The elbow and the shoulder joints
were free to move in their anatomical range of motion. The mechanism
included built-in mechanical constraints which kept the exoskeleton joint
angles within the average human anthropometric boundaries. Since the human
arm and the exoskeleton were mechanically linked the movements of the
forearms and the upper arm of both the human and the exoskeleton were
identical.
The basic purpose of the exoskeleton system as an assistance device is to
amplify the moment generated by the human muscles relative to the elbow
joint, while manipulating loads. The exoskeleton's elbow and shoulder joints
were powered by a DC servo motor (ESCAP-35NT2R82) with a stall torque of 360
mNm equipped with a planetary gearbox (ESCAP-R40) with a gear ratio of 1:193
and a maximal output torque of 40 Nm. An optical incremental shaft encoder
(HP HEDS 5500) with 500 lines was attached to the motor shaft. Due to the
encoder location and the high gear ratio, the practical encoder's resolution
for measuring the joint angle was 0.0036 Deg. This setup incorporated a DC
motor with the highest torque-to-weight ratio that was available on the
commercial market at that time with a power consumption that could be
provided by a battery. A high energy density of the power supply and an
actuator with a high torque-to-weight ratio are two key features of the
exoskeleton system as a self contained mobile medical assistance device for
the disabled community. Limits imposed by present technology on these two
key components along with design requirements for developing a compact
system with a potential of serving as a medical assistance device for
disabled person restricted the payload to be 5 Kg. However, this biomedical
oriented design does not restrict the generality of the exoskeleton concept
or its operational algorithms. Using other actuation systems, like hydraulic
system increases the load capacity substantially.
The exoskeleton forearm was extended by a rod with a special connector for
attaching disk-type weights (external load). Four force sensors (TEDEA 1040)
were mounted at the interfaces between the exoskeleton and the operator, one
at the tip carrying the external load, two between the exoskeleton and the
human hand and one at the interface between the upper arm and the
exoskeleton. The first load cell, inserted between the rod holding the
external load and the exoskeleton forearm link, measured the actual shear
force, normal to the forearm axis, applied by the external load. The other
load cells were installed between the handle grasped by the human hand and
the forearm link of the exoskeleton and between the upper arm bracelet and
the exoskeleton upper link. These load cells measured the shear forces
applied by the operator to the mechanism. Multiplying the sensors'
measurements by the corresponding moment arms indicated the moments applied
by the weights and by the human arm relative the elbow and the shoulder
joints.Surface EMG electrodes (8 mm Ag-AgCl BIOPAC - EL208S) were
attached to the subject’s skin by adhesive disks for measuring the EMG
signal of the Biceps Brachii and Triceps Brachii medial-head muscles. The
signals were gained by EMG amplifiers (BIOPAC - EMG100A) using a gain factor
in the range of 2000-5000 (depending on the subject). The EMG signals and
the load cell signal were acquired by an A/D convector (Scientific Solution
Lab Master 12 bit internal PC card) with a 1 kHz sampling rate, whereas the
encoder signals were counted by custom-made hardware. The entire data set
was recorded simultaneously and stored, for later off-line analysis and
simulation.
A special real-time software, for operating the system, was written in C and
run on a PC-based platform. The software was composed of three main modules.
The first module dealt with the hardware/software interface. It controlled
the interaction between the PC and the external motor driver and the
sensors, through a D/A and an A/D card. The second module included the
automatic code generated by the MATLAB - Simulink Real-Time toolbox. The
third module was the user interface module which allowed to set various run
time operational parameters. All the modules were compiled and linked for
generating an efficient real-time software.
Exoskeleton Prototype 3 (EXO-UL3)
- Integrating human and robot into a single system offers
remarkable opportunities for creating a new generation of assistive
technology for both healthy and disabled people. Humans possess naturally
developed algorithms for control of movement, but they are limited by their
muscle strength. In addition, muscle weakness is the primary cause of
disability for most people with neuromuscular diseases and injuries to the
central nervous system. In contrast, robotic manipulators can perform tasks
requiring large forces; however, their artificial control algorithms do not
provide the flexibility to perform in a wide range of fuzzy conditions while
preserving the same quality of performance as humans. It seems therefore
that combining these two entities, the human and the robot, into one
integrated system under the control of the human, may lead to a solution
that will benefit from the advantages offered by each subsystem.
The exoskeleton robot, serving as an assistive device, is worn by the human
(orthotic) and functions as a human-amplifier. Its joints and links
correspond to those of the human body, and its actuators share a portion of
the external load with the operator. One of the primary innovative ideas of
the proposed research is to set the Human Machine Interface (HMI) at the
neuromuscular level of the human physiological hierarchy using the body's
own neural command signals as one of the primary command signals of the
exoskeleton. These signals will be in the form of processed surface
electromyography (sEMG) signals, detected by surface electrodes placed on
the operator's skin. The proposed HMI takes advantage of the
electro-chemical-mechanical delay, which inherently exists in the
musculoskeletal system, between the time when the neural system activates
the muscular system and the time when the muscles generate moments around
the joints. The myoprocessor is a model of the human muscle running in
real-time and in parallel to the physiological muscle. During the
electro-chemical-mechanical time delay, the system will gather information
regarding the physiological muscle’s neural activation level based on
processed sEMG signals, the joint position, and angular velocity, and will
predict using the myoprocessor the force that will be generated by the
muscle before physiological contraction occurs. By the time the human
muscles contract, the exoskeleton will move with the human in a synergistic
fashion, allowing natural control of the exoskeleton as an extension of the
operator's body.
The goal of this research is to design, build, and study the integration of
a powered exoskeleton controlled by myosignals for the human arm. The
research will pursue this goal through several objectives: (i) developing an
8 degrees of freedom powered anthropomorphic exoskeleton for the arm,
including grasping/releasing; (ii) setting the HMI at the neuromuscular
level by using processed sEMG signals as the primary command signal to the
exoskeleton system; (iii) developing muscle models (myoprocessor) for
predicting the human arm joints' torques; (iv) developing control algorithms
that will fuse information from multiple sensors and will guarantee stable
exoskeleton operation; (v) evaluating the overall performance of the
integrated system using standardized arm/hand function tests. These goals
and objectives will be pursued using several experimental protocols aimed at
developing the myoprocessors and evaluating the exoskeleton performance. The
proposed experimental protocol includes only healthy subjects as the first
step in a long-term goal aimed to evaluate the exoskeleton performance with
disabled subjects suffering from various neurological disabilities, such as
stroke, spinal cord injury, muscular dystrophies, and other
neurodegenerative disorders.
It is anticipated that the proposed research will advance the current
knowledge in the field of modeling human muscles and their mathematical
formulation. This knowledge will be further used to create a novel HMI and
will permit a better understanding of the interaction between human and
robot at the neural level. In addition, the proposed research will provide a
tool and fundamental understanding regarding the development of an assistive
technology for improving the quality of life of the disabled community. The
proposed scientific activity will promote interdisciplinary collaboration
between students and faculty members from the fields of electrical
engineering, mechanical engineering, bioengineering, and rehabilitation
medicine.