LOPES (exoskeleton)
Encyclopedia
The goal of the LOPES project (LOwer-extremity Powered ExoSkeleton) is to design and implement
a gait rehabilitation
robot
for treadmill
training. The target group consists of people who have
suffered a stroke
and have impaired motor control
.
The main goals of LOPES are:
The mechanical construction should offer assistance in leg movements in the forward direction
and in keeping lateral balance. Within the LOPES project, it has been decided to realize this
by connecting the limbs of the patient to an exoskeleton
so that robot and patient move in parallel.
Most gait rehabilitation robots that are currently being developed [1, 2] focus on the support of the
entire gait cycle as a single unit. These robots use joint trajectories of the entire gait cycle and
offer a uniform (more or less) stiff control along this trajectory. This means that the patient
receives support in gait phases where support is necessary but also in phases where support isn’t
necessary. Studies have been done on an exoskeleton [3] that propose adaptive control methods which
minimize the interaction forces with the patient with respect to an adaptable reference pattern,
but these still control the entire gait cylce. Studies have also shown that walking with the current
lokomat frame requires significantly less energy than normal walking [4]. This means that patients
are not walking as actively as possible but are able to walk a greater distance. LOPES aims to support
and not take over those tasks that the patient is unable to perform without help using an impedance
control scheme. This will lead to a more active participation from the patient’s side. The tradeoff
for more active walking will likely be a smaller overall distance during therapy sessions. The
implication of selective function support is that the robot will have two extreme modes in which it
should be able to function, these are:
Currently the first prototype has been completed. This prototype has 8 actuated DOF (series elastic actuation) following the design as in [5]. Clinical evaluations will be done in the course of 2007.
a gait rehabilitation
Physical therapy
Physical therapy , often abbreviated PT, is a health care profession. Physical therapy is concerned with identifying and maximizing quality of life and movement potential within the spheres of promotion, prevention, diagnosis, treatment/intervention,and rehabilitation...
robot
Robot
A robot is a mechanical or virtual intelligent agent that can perform tasks automatically or with guidance, typically by remote control. In practice a robot is usually an electro-mechanical machine that is guided by computer and electronic programming. Robots can be autonomous, semi-autonomous or...
for treadmill
Treadmill
A treadmill is an exercise machine for running or walking while staying in one place. The word treadmill traditionally refers to a type of mill which was operated by a person or animal treading steps of a wheel to grind grain...
training. The target group consists of people who have
suffered a stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
and have impaired motor control
Motor control
Motor control are information processing related activities carried out by the central nervous system that organize the musculoskeletal system to create coordinated movements and skilled actions...
.
The main goals of LOPES are:
- Reduction of the physical load on the therapistPhysical therapyPhysical therapy , often abbreviated PT, is a health care profession. Physical therapy is concerned with identifying and maximizing quality of life and movement potential within the spheres of promotion, prevention, diagnosis, treatment/intervention,and rehabilitation...
/ patientPatientA patient is any recipient of healthcare services. The patient is most often ill or injured and in need of treatment by a physician, advanced practice registered nurse, veterinarian, or other health care provider....
; - More efficient gaitGait (human)Human gait is the way locomotion is achieved using human limbs. Different gaits are characterized by differences in limb movement patterns, overall velocity, forces, kinetic and potential energy cycles, and changes in the contact with the surface .- Foot strike :One variable in different gaits is...
training for stroke patients; - Selective support of gait functions;
- Therapist stays in charge of high-level decisions.
The mechanical construction should offer assistance in leg movements in the forward direction
and in keeping lateral balance. Within the LOPES project, it has been decided to realize this
by connecting the limbs of the patient to an exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
so that robot and patient move in parallel.
Most gait rehabilitation robots that are currently being developed [1, 2] focus on the support of the
entire gait cycle as a single unit. These robots use joint trajectories of the entire gait cycle and
offer a uniform (more or less) stiff control along this trajectory. This means that the patient
receives support in gait phases where support is necessary but also in phases where support isn’t
necessary. Studies have been done on an exoskeleton [3] that propose adaptive control methods which
minimize the interaction forces with the patient with respect to an adaptable reference pattern,
but these still control the entire gait cylce. Studies have also shown that walking with the current
lokomat frame requires significantly less energy than normal walking [4]. This means that patients
are not walking as actively as possible but are able to walk a greater distance. LOPES aims to support
and not take over those tasks that the patient is unable to perform without help using an impedance
control scheme. This will lead to a more active participation from the patient’s side. The tradeoff
for more active walking will likely be a smaller overall distance during therapy sessions. The
implication of selective function support is that the robot will have two extreme modes in which it
should be able to function, these are:
- Patient in charge: The goal of the robot is to minimize the interaction forces between the patient and the robot in order for the patient to walk freely without feeling the robot. This mode will be active mostly for the non-paretic side of the patient and during those phases of the walking cycle that the robot does not need to assist.
- Robot in charge: The goal of this mode is to take control of the patient. The robot will take over the functions which the patient is unable to perform. The robot will most likely operate somewhere between these extremes offering some support at those phases when it is needed to guide the patient towards desirable behavior.
Currently the first prototype has been completed. This prototype has 8 actuated DOF (series elastic actuation) following the design as in [5]. Clinical evaluations will be done in the course of 2007.