Brian Weinberg

Design, Control and Human Testing of an Active Knee Rehabilitation Orthotic Device

This paper presents a novel, smart and portable active knee rehabilitation orthotic device (AKROD) designed to train stroke patients to correct knee hyperextension during stance and stiff-legged gait (defined as reduced knee flexion during swing). The knee brace provides variable damping controlled in ways that foster motor recovery in stroke patients. A resistive, variable damper, electro-rheological fluid (ERF) based component is used to facilitate knee flexion during stance by providing resistance to knee buckling. Furthermore, the knee brace is used to assist in knee control during swing, i.e. to allow patients to achieve adequate knee flexion for toe clearance and adequate knee extension in preparation to heel strike. The detailed design of AKROD, the first prototype built, closed loop control results and initial human testing are presented here

Control of electro-rheological fluid based resistive torque elements for use in active rehabilitation devices

In this paper we present control algorithms for novel electro-rheological fluid based resistive torque generation elements that will be used to drive the joint of a new type of portable and controllable active knee rehabilitation orthotic device (AKROD) for iso-inertial, isokinetic, and isometric exercising as well as gait retraining. The AKROD is composed of straps and rigid components for attachment to the leg, with a central hinge mechanism where a gear system is connected. The key features of AKROD include: a compact, lightweight design with highly tunable torque capabilities through a variable damper component, full portability with on-board power, control circuitry, and sensors (encoder and torque), and real-time capabilities for closed loop computer control for optimizing gait retraining. The variable damper component is achieved through an electro-rheological fluid (ERF) element that connects to the output of the gear system. Using the electrically controlled rheological properties of ERFs, compact brakes capable of supplying high resistive and controllable torques are developed. In this project, a prototype for the AKROD has been developed and tested. The AKRODs ERF resistive actuator was tested in laboratory experiments using a custom-made ERF testing apparatus (ETA). ETA provides a computer-controlled environment to test ERF brakes and actuators in various conditions and scenarios including emulating the interaction between human muscles involved with the knee and the AKRODs ERF actuators/brakes. The AKRODs ERF resistive actuator was tested in closed loop torque control experiments. A hybrid (non-linear, adaptive) proportional-integral (PI) torque controller was implemented to achieve this goal.

fMRI-compatible rehabilitation hand device

BackgroundFunctional magnetic resonance imaging (fMRI) has been widely used in studying human brain functions and neurorehabilitation. In order to develop complex and well-controlled fMRI paradigms, interfaces that can precisely control and measure output force and kinematics of the movements in human subjects are needed. Optimized state-of-the-art fMRI methods, combined with magnetic resonance (MR) compatible robotic devices for rehabilitation, can assist therapists to quantify, monitor, and improve physical rehabilitation. To achieve this goal, robotic or mechatronic devices with actuators and sensors need to be introduced into an MR environment. The common standard mechanical parts can not be used in MR environment and MR compatibility has been a tough hurdle for device developers.MethodsThis paper presents the design, fabrication and preliminary testing of a novel, one degree of freedom, MR compatible, computer controlled, variable resistance hand device that may be used in brain MR imaging during hand grip rehabilitation. We named the device MR_CHIROD (M agnetic R esonance C ompatible Smart H and I nterfaced R ehabilitation D evice). A novel feature of the device is the use of Electro-Rheological Fluids (ERFs) to achieve tunable and controllable resistive force generation. ERFs are fluids that experience dramatic changes in rheological properties, such as viscosity or yield stress, in the presence of an electric field. The device consists of four major subsystems: a) an ERF based resistive element; b) a gearbox; c) two handles and d) two sensors, one optical encoder and one force sensor, to measure the patient induced motion and force. The smart hand device is designed to resist up to 50% of the maximum level of gripping force of a human hand and be controlled in real time.ResultsLaboratory tests of the device indicate that it was able to meet its design objective to resist up to approximately 50% of the maximum handgrip force. The detailed compatibility tests demonstrated that there is neither an effect from the MR environment on the ERF properties and performance of the sensors, nor significant degradation on MR images by the introduction of the MR_CHIROD in the MR scanner.ConclusionThe MR compatible hand device was built to aid in the study of brain function during generation of controllable and tunable force during handgrip exercising. The device was shown to be MR compatible. To the best of our knowledge, this is the first system that utilizes ERF in MR environment.

Active Knee Rehabilitation Orthotic Device With Variable Damping Characteristics Implemented via an Electrorheological Fluid

This paper presents a novel, smart, and portable active knee rehabilitation orthotic device (AKROD) that provides variable damping at the knee joint, controlled in ways that can facilitate motor recovery in poststroke and other neurological disease patients, and to accelerate recovery in knee injury patients. The key features of AKROD include a compact, lightweight design, with highly tunable resistive torque capabilities through a variable damper component that is achieved through an electrorheological fluid (ERF) smart brake. Closed-loop torque and velocity controllers based on adaptive nonlinear control methodologies were developed and successfully implemented on the ERF brake. Preliminary testing of AKROD was performed using nine healthy subjects executing a set of isokinetic and isotonic exercises. These results were compared with exactly the same tests performed on a modern day computer controlled rehabilitation resistance machine, a Biodex System 3. The results showed comparable accuracy and repeatability between the two devices.

MR_CHIROD v.2: Magnetic Resonance Compatible Smart Hand Rehabilitation Device for Brain Imaging

This paper presents the design, fabrication, and testing of a novel, one degree-of-freedom, magnetic resonance compatible smart hand interfaced rehabilitation device (MR_CHIROD v.2), which may be used in brain magnetic resonance (MR) imaging during handgrip rehabilitation. A key feature of the device is the use of electrorheological fluids (ERFs) to achieve computer controlled, variable, and tunable resistive force generation. The device consists of three major subsystems: 1) an ERF based resistive element, 2) handles, and c) two sensors, one optical encoder and one force sensor, to measure the patient induced motion and force. MR_CHIROD v.2 is designed to resist up to 50% of the maximum level of gripping force of a human hand and be controlled in real time. Our results demonstrate that the MR environment does not interfere with the performance of the MR_CHIROD v.2, and, reciprocally, its use does not cause fMR image artifacts. The results are encouraging in jointly using MR_CHIROD v.2 and brain MR imaging to study motor performance and assess rehabilitation after neurological injuries such as stroke.

RehAbilitative Knee Orthosis Driven by Electro-Rheological Fluid Based Actuators

This work aims to demonstrate the feasibility of using Electro-Rheological Fluid (ERF) actuators in orthotics, creating a new breed of rehabilitation devices. ERFs are fluids that experience dramatic changes in rheological properties, such as viscosity or yield stress, in the presence of an electric field. Using the electrically controlled rheological properties of ERFs, compact actuators with an ability to supply high resistive torques in a controllable and tunable fashion, have been developed. This study involves the design, fabrication and testing of an ERF based knee orthotic device and the innovative ERF actuators it uses. The knee orthotic is achieved through a standard brace design with a polycentric hinge and gear system. Coupled to this are two Flat-Plate ERF actuators, given that name for their characteristic set of parallel flat plates allowing for actuation of the fluid. A full model describing the field dependant torque output of these actuators is presented along with a full detailed description of the device design. The overall knee orthotic system is designed to resist up to 25.4% of an average human knee’s torque abilities and be controlled in real-time. The goal of this work is to provide a much more efficient means of rehabilitation over the average orthotic, while matching the proficiency of rehabilitation machines, all in a smaller, simpler, and more cost efficient design.

MR compatible ERF driven hand rehabilitation device

This paper presents the design, fabrication and preliminary tests of a novel, one degree of freedom, MR compatible, computer controlled, variable resistance hand device that will be used in fMRI studies of the brain and motor performance during rehabilitation after stroke. The device consists of four major subsystems: a) the electro-rheological fluid (ERF) resistive element; b) the gearbox; c) the handles and d) the sensors: one optical encoder and one force sensor attached to the ERF resistive elements shaft to measure the patient induced motion and force, respectively. A key feature of the device is the use of electro theological fluids (ERF) to achieve resistive force generation. ERFs are fluids that experience dramatic changes in rheological properties, such as viscosity or yield stress, in the presence of an electric field. Using the electrically controlled rheological properties of ERFs, compact resistive elements with an ability to supply high resistive torques in a controllable and tunable fashion, have been developed. Our preliminary tests demonstrate that the device can apply, on a human hand holding the device handles, resistive forces that exceed 150 N. In addition the activated ERF maintain its properties in the magnetic environment without creating degradation of the MR images. The results are encouraging in combining functional magnetic resonance imaging methods, with MR compatible robotic devices for improved effectiveness of rehabilitation therapy.

Design and control of a robotic lower extremity exoskeleton for gait rehabilitation

Design and control of an active knee rehabilitation orthotic system called ANdROS that was designed as a wearable and portable gait rehabilitation tool is presented. A corrective force field that reinforces a desired gait pattern is applied to the patients impaired leg around the knee joint via an impedance controlled exoskeleton. The impedance controller is synchronized with the patients walking phase which is estimated from the kinematic measurements of the healthy leg. The performance of the controller is evaluated through bench-testing.

Evaluation of Electrorheological Fluid Dampers for Applications at 3-T MRI Environment

This paper evaluates the use of electrorheological fluids (ERFs) within a magnetic resonance imaging (MRI) environment. ERF is a semiactive variable impedance material, which could be used as an alternative type of resistive force/torque generation or in combination with other actuators as a damper/clutch to modulate the output force/torque of the actuator. In this paper, an ERF damper/brake is introduced and its magnetic resonance (MR) compatibility is examined at a 3-T MR imaging environment by measuring the output performance of the damper and the SNR of the MRI images. The experimental results showed that dampers resistive force generation while positioned within the MRI is almost the same as that in normal operation. The signal-to-noise investigation was performed both with a phantom and human. The results indicated that the ERF damper did not affect the MRI images when it was operated over 30 cm away from the MRIs RF coil. We hope that the synthesis and tables presented in this paper can facilitate the choice of ERF brake actuation principle to various applications in an MR environment.

Electro-rheological fluidic actuators for haptic vehicular instrument controls

Force-feedback mechanisms have been designed to simplify and enhance the human-vehicle interface. The increase in secondary controls within vehicle cockpits has created a desire for a simpler, more efficient human-vehicle interface. By consolidating various controls into a single, haptic feedback control device, information can be transmitted to the operator, without requiring the drivers visual attention. In this paper Electro-Rheological Fluids (ERF) based actuated mechanisms are presented that provide haptic feedback ERFs are liquids that respond mechanically to electric fields by changing their properties, such as viscosity and shear stress electroactively. Using the electrically controlled rheological properties of ERFs, we developed haptic devices that can resist human operator forces in a controlled and tunable fashion. The design of two types of ERF-based actuators and joystick is presented in detail. Their analytical model is derived, parametric analysis is performed, and experimental systems and data are presented.