US-12616590-B2 - Assistive device with hybrid control systems

US12616590B2US 12616590 B2US12616590 B2US 12616590B2US-12616590-B2

Abstract

An assistive device is disclosed that includes a plurality of control systems for controlling active and passive tasks. The assistive device accommodates active power generation when needed, but is otherwise configured to switch to passive control for other tasks. The assistive device further includes a continuously variable transmission to optimize movement of the assistive device for a variety of tasks. The assistive device includes a lower limb embodiment defining an artificial knee joint controlled by the plurality of control systems.

Inventors

Tom Pickerill
James Lipsey

Assignees

REHABILITATION INSTITUTE OF CHICAGO

Dates

Publication Date: 20260505
Application Date: 20201207

Claims (19)

1 . An assistive device with hybrid control systems, comprising: a knee joint; one or more actuating components for actuating the knee joint; a plurality of sensors positioned along the one or more actuating components that provide feedback data associated with the knee joint; a hybrid control system defined along the knee joint and in operable communication with the plurality of sensors, including: an active control system that provides net positive energy, and a passive control system that varies power dissipated at the knee joint to accommodate net zero or negative energy; a variable transmission mechanism defined by the one or more actuating components that adjusts a mechanical transmission ratio to optimize a mechanical power profile of the knee joint for predetermined active and passive tasks; a dynamic braking control mechanism configured for varying an amount of braking of the one or more actuating components in real time, comprising: a plurality of transistor pairs for braking control, each of the plurality of transistor pairs including an enhancement mode transistor and a depletion mode transistor, the plurality of transistor pairs engageable for unique braking conditions, and a pulse wave associated with the passive control system defining a duty cycle adjustable by the processing device to provide responsive control of the amount of braking; and a processing device in operable communication with the plurality of sensors and the hybrid control system, the processing device configured to determine a state of the knee joint based on the feedback data and engage either or both of the active control system or the passive control system based on the state of the knee joint.
2 . The assistive device of claim 1 , wherein, based on a change in the state of the knee joint, the processing device is configured to engage the active control system to perform a first set of mechanical functions, and the processing device is configured to disengage the active control system and is configured to engage the passive control system to perform a second set of mechanical functions to minimize consumption of electrical energy.
3 . The assistive device of claim 1 , wherein the passive control system utilizes rheostatic dynamic braking to dissipate electrical energy as thermal energy through windings of a motor of the one or more actuating components which resists motion of the knee joint.
4 . The assistive device of claim 1 , wherein the active control system utilizes impedance control, which includes acceptance of a desired knee joint angle, stiffness and dampening as inputs from the processing device to calculate a desired motor current.
5 . The assistive device of claim 1 , wherein the passive control system accepts a desired knee joint angle and two braking factors as inputs from the processing device to calculate a desired braking parameter for a motor of the one or more actuating components.
6 . The assistive device of claim 1 , wherein the one or more actuating components comprises: a first motor for converting electrical energy to mechanical energy as rotational motion; a roller screw that receives and converts the rotational motion from the first motor to linear motion; and a slider crank assembly that converts the linear motion back to rotational motion at the knee joint, including: a crank, and a connecting rod, including a first end engaged to a nut of the roller screw at a first rod pivot, and a second end of the connecting rod engaged to the crank at a second rod pivot, the nut of the roller screw transmitting the linear motion through the connecting rod to the second rod pivot to rotate the crank about an axis.
7 . The assistive device of claim 6 , wherein the variable transmission mechanism modified a transmission ratio of the slider crank assembly by changing a distance between the first rod pivot and the second rod pivot based on the state of the knee joint which accommodates speed and torque specifications of the one or more actuating components predetermined to be suitable for the state of the knee joint.
8 . The assistive device of claim 6 , wherein the plurality of sensors includes encoders for measuring knee joint angle position and a first motor position to measure a crank moment arm length.
9 . The assistive device of claim 1 , wherein the plurality of sensors includes a load cell that measures ground level reaction forces and moments, and an inertial measurement unit (IMU) that measures knee joint acceleration and inclination angles.
10 . The assistive device of claim 1 , wherein the pulse wave is transmitted to a gate of the plurality of transistor pairs which in turn modulates a knee joint braking output.
11 . The assistive device of claim 10 , wherein each transistor of the plurality of transistor pairs couples an electromagnetic coil of a first motor with a ground voltage line.
12 . The assistive device of claim 11 , wherein the first motor is configured to prevent rotating when a high logic level is applied to the plurality of transistor pairs and wherein net positive power is applied to the first motor when a low logic level is applied to the enhancement mode transistors.
13 . The assistive device of claim 12 , wherein the enhancement mode transistor closes when a high logic level of the pulse wave is applied to the gate of each enhancement mode transistor thereby grounding each of the electromagnetic coils and generating a back electromagnetic force preventing rotation of the first motor.
14 . The assistive device of claim 12 , wherein the enhancement mode transistor is configured to open when a low logic level of the pulse wave is applied to the gate of each enhancement mode transistor thereby enabling a signal from the active control system to control the rotation of the first motor.
15 . The assistive device of claim 12 , wherein the depletion mode transistor is configured to open when power is supplied to the assistive device.
16 . The assistive device of claim 12 , wherein the depletion mode transistor is configured to close when power is not supplied to the assistive device, thereby grounding each of the electromagnetic coils and generating a back electromagnetic force preventing rotation of the first motor.
17 . The assistive device of claim 16 , wherein an impedance between the depletion mode transistor and the electromagnetic coils is configured for preselection in order to vary a strength of the back electromagnetic force preventing rotation of the first motor when power is not applied to the assistive device.
18 . A system for substituting a joint of the human body, comprising: an assistive device including a joint, one or more actuating components for engaging the joint, and a plurality of sensors; a hybrid control system for controlling the assistive device, including: an active control system that provides net positive energy, and a passive control system that varies power dissipated at the joint to accommodate net zero or negative energy, and a variable transmission mechanism defined by the one or more actuating components that adjusts a mechanical transmission ratio to optimize a mechanical power profile of the one or more actuating components for predetermined active and passive tasks; a dynamic braking control mechanism configured for varying an amount of braking of the one or more actuating components in real time, comprising: a plurality of transistor pairs for braking control, each of the plurality of transistor pairs including an enhancement mode transistor and a depletion mode transistor, the plurality of transistor pairs engageable for unique braking conditions, and a pulse wave associated with the passive control system defining a duty cycle adjustable by the processing device to provide responsive control of the amount of braking; and a processing device in operable communication with the plurality of sensors and the hybrid control system, the processing device configured to determine a state of the joint and engage either or both of the active control system or the passive control system.
19 . A method of manufacturing an assistive device, comprising: forming an assistive device including one or more actuating components and a plurality of sensors; and forming a hybrid control system that receives data from the plurality of sensors and includes a processing element for controlling the assistive device, including: forming an active control system that provides net positive energy, forming a passive control system that varies power dissipated at a joint to accommodate net zero or negative energy, and forming a dynamic braking control mechanism configured for varying an amount of braking of the one or more actuating components in real time, comprising: a plurality of transistor pairs for braking control, each of the plurality of transistor pairs including an enhancement mode transistor and a depletion mode transistor, the plurality of transistor pairs engageable for unique braking conditions, and a pulse wave associated with the passive control system defining a duty cycle adjustable by the processing device to provide responsive control of the amount of braking, wherein the processing element is configured to determine a state of the joint and engage either or both of the active control system or the passive control system.

Description

CROSS REFERENCE TO RELATED APPLICATIONS The present document is a non-provisional application that claims benefit to U.S. Provisional Application Ser. No. 62/943,913, filed on Dec. 5, 2019, which is herein incorporated by reference in its entirety. FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT The invention was made with government support under National Institute on Disability, Independent Living, and Rehabilitation Research (NIDILRR) award nos. 90REGE0003 and 90RE5014 and National Institutes of Health (NIH) award no. 2R01HD079428. The government has certain rights in the invention. FIELD The present disclosure is generally directed to prosthetic and rehabilitation devices; and more specifically, to an assistive device configured for hybrid control that includes an active control system and a passive control system and is adapted to switch to either control system as needed for a given task. BACKGROUND With most commercially available lower limb prostheses, there is a common tradeoff between function and weight. Passive devices, which make up a majority of commercial knee prosthesis, are designed with constant or variable resistances at the joint level. They are lightweight, quiet and robust, but provide only limited function. Powered prosthetic knees on the other hand provide net positive power to assist with stairs and getting up from a seated position. However, they are inefficient during walking and standing, can be too slow for faster walking, and come at the cost of significant added weight. There is a need for a prosthetic knee that does not compromise on function or weight, which provides power for tasks when needed, and is lightweight and small enough to be used comfortably by a wider range of amputees. It is with these observations in mind, among others, that various aspects of the present disclosure were conceived and developed. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustration of the phases of gait as referenced in the present disclosure. FIG. 2A is a simplified block diagram of a system including a general assistive device with hybrid passive and active control systems described herein. FIG. 2B is an illustration of a cross-sectional view of one particular embodiment of the assistive device of FIG. 2A taking the form of a lower limb assistive device. FIG. 2C is an illustration of a cross sectional view of the embodiment of FIG. 2B demonstrating a change in knee joint angle. FIG. 3 is another illustration of a cross-sectional view of the lower limb assistive device of FIG. 2B highlighting a slider crank mechanism. FIG. 4 is another illustration of a cross-sectional view of the lower limb assistive device of FIG. 2B highlighting possible electronics hardware. FIG. 5 is an illustration of an equation for computing a transmission ratio calculation as referenced in the present disclosure. FIG. 6 is an illustration of a three-dimensional (3D) graph demonstrating transmission ratio vs. crank moment arm length and knee joint position as referenced in the present disclosure. FIG. 7 is an illustration of an overview for control system hardware of the assistive device described herein. FIG. 8 is an illustration of a “passive” control system overview associated with the assistive device described herein. FIG. 9 is an illustration of an “active” control system overview associated with the assistive device described herein. FIG. 10 is an illustration of a basic impedance control equation which may be implemented as described herein. FIG. 11 is an illustration of a modified proportional derivative (PD) control equation which may be implemented as described herein. FIG. 12 is an illustration of a pulse width modulation duty cycle as referenced herein. FIGS. 13A-13B are front and back view respectively of a custom control PCB for dynamic braking control as referenced herein. FIG. 14 is a graph illustrating 5th order polynomial fit for duty cycle v. braking percentage. Corresponding reference characters indicate corresponding elements among the view of the drawings. The headings used in the figures do not limit the scope of the claims. DETAILED DESCRIPTION Aspects of the present disclosure relate to embodiments of an assistive device controlled by a plurality of control systems selectively engaged for active and/or passive tasks. In some embodiments, the assistive device includes a continuous variable transmission, and dynamic braking control such that the device is optimized for a wider range of tasks. The assistive device is energy efficient, yet suitable for adaptation to the task at hand. The assistive device may be embodied as a lower limb assistive device, and may include any number of actuating components for operating a knee joint (i.e., artificial joint resembling a natural knee), including both active and passive tasks, as described herein. Turning to the drawings, wherein like reference numerals refer to like elements, the present disclosure is illustrated as being implemented in a suitable e