TWI901483B - Upper limb exoskeleton device with safe operation function - Google Patents

Abstract

The present invention is an upper limb exoskeleton device with a safe operation function, comprising: a main body having a back structure and a second hand structure, wherein the second hand structure has a shoulder joint unit and an elbow joint unit respectively; the shoulder joint unit; two angle sensors, respectively disposed on the shoulder joint unit, for sensing the rotation angle of the shoulder joint unit; two drive motors, respectively disposed on the back structure, through two series of A flexible actuator and two drive lines are connected to the second hand structure, driving the shoulder joint unit of the second hand structure to rotate. A power supply unit supplies the power required for the operation of various components of the upper limb exoskeleton device. A control interface, worn by the user, is used to send control commands. A main controller unit, located on the back structure, receives the rotation angle signal from the angle sensor and the control command to control the drive motor.

Description

Upper limb exoskeleton device with safe operation function

This invention relates to wearable exoskeleton technology, and in particular to an upper limb exoskeleton device with safe operation capabilities that can improve the safety and energy efficiency of active upper limb exoskeletons while providing assistance and compliance (safety).

Upper-limb exoskeletons are primarily classified into two types: passive and active. Passive upper-limb exoskeletons utilize energy storage elements such as springs to provide passive assistance. Compared to active upper-limb exoskeletons, they generally provide less assistive torque but are less expensive. Active upper-limb exoskeletons utilize high-power density motors/actuators for assistance. Software algorithms can switch between different modes for different application scenarios, allowing the exoskeleton to adapt to a wider range of work environments. However, battery life may limit their operating time, and there are fewer software-based safety controls.

Existing technologies have not addressed how to design an upper-limb exoskeleton device that simultaneously balances assistance, compliance (comfort), and safety. Furthermore, they have not addressed how active upper-limb exoskeletons can address safety concerns and power-limited usage time caused by the hands being restrained by the exoskeleton due to system failures.

To address the shortcomings of prior art, the present invention provides an upper limb exoskeleton device with safe operation capabilities. This device can provide assistance and compliance (safety) while improving the safety and energy efficiency of active upper limb exoskeletons.

The present invention is an upper limb exoskeleton device with a safe operation function, comprising: a main body, which is worn on the upper body of a user, and has a back structure and a second hand structure, the second hand structure being respectively arranged on both sides of the back structure, and the second hand structure having a shoulder joint unit and an elbow joint unit; two angle sensors, which are respectively arranged on the shoulder joint unit, for sensing the rotation angle of the shoulder joint unit; two drive motors, which are arranged on the back structure, and are respectively connected to the second hand structure through two series elastic actuators and two drive lines. The upper limb exoskeleton comprises a rotational mechanism and drives the shoulder joint unit of the second hand structure to rotate; a power unit supplies the power required for the operation of various components of the upper limb exoskeleton device; a control interface, worn by the user, is used to send control commands; a main controller unit, located on the back structure, receives the rotation angle signal from the angle sensor and the control command to control the drive motor; the main controller adjusts the system stiffness and damping parameters of the upper limb exoskeleton device in real time based on an admittance model to reduce the risk of injury to the user due to component failure.

In one embodiment of the present invention, the drive motor is a brushless DC motor (BLDC).

In one embodiment of the present invention, one or more additional degree-of-freedom units, such as bearings, joints, etc., may be provided at the connection between the second hand structure and the back structure, or at the shoulder joint unit.

In one embodiment of the present invention, the elbow joint unit is provided with a torsion spring.

In one embodiment of the present invention, a pawl and a ratchet are provided between the drive motor and the series elastic actuator to lock or unlock the drive wire of the drive motor.

In one embodiment of the present invention, the control interface is a touch controller using a touch screen or control buttons.

In one embodiment of the present invention, the control interface is a voice controller for receiving voice commands from the user.

In one embodiment of the present invention, information is transmitted between the control interface and the main controller unit via Bluetooth or other wireless transmission methods.

In one embodiment of the present invention, the drive line is a rope, chain, belt or other type of flexible transmission device.

In one embodiment of the present invention, the main controller unit communicates with and controls the angle sensor and the drive motor via the CAN bus.

The above overview and the following detailed description and accompanying figures are intended to further illustrate the methods, means, and effects of this invention in achieving its intended purpose. Other objects and advantages of this invention will be elaborated upon in the subsequent description and illustrations.

10: Body

11: Back structure

12: Hand structure

12A: Shoulder joint unit

12B: Elbow joint unit

13: Angle sensor

14: Driving motor

141: Series elastic actuator

142: Drive Line

14A: Pawl and ratchet module

15: Power supply unit

16: Control Interface

17: Main controller unit

Figure 1 is a schematic structural diagram of an embodiment of an upper limb exoskeleton device with safe operation capabilities according to the present invention.

Figure 2 is a schematic diagram of the signal waveform of the security issue that this invention aims to solve.

The following describes the implementation of the present invention using specific examples. Those skilled in the art can easily understand the other advantages and effects of the present invention from the contents disclosed in this specification.

FIG1 is a schematic diagram of an embodiment of an upper limb exoskeleton device with a safe operation function of the present invention. The embodiment comprises: a body 10, which is worn on the upper body of a user, and has a back structure 11 and a second hand structure 12. The second hand structures are symmetrically arranged on both sides of the back structure 11 to adapt to the back-shoulder-hand area of the user (human body). The second hand structure 12 has a shoulder The shoulder joint unit 12A and an elbow joint unit 12B, the shoulder joint unit 12A can be additionally provided with one or more degree of freedom elements, the elbow joint unit 12B is provided with a torsion spring; two angle sensors 13 are respectively provided inside the shoulder joint unit 12A for sensing the rotation angle of the shoulder joint unit 12A; two drive motors 14 are provided on the back structure 11, respectively through two series elastic actuators 141 and two drive lines 142 are connected to the second hand structure 12, and drive the shoulder joint unit 12A of the second hand structure 12 to rotate. The drive motor 14 is provided with a pawl and ratchet module 14A, which can be used to lock or unlock the drive line 142; a power unit 15 is used to supply the power required for the operation of each component of the upper limb exoskeleton device; a control interface 16 is a wearable interface, which can be a voice or touch interface. The upper limb exoskeleton comprises a main controller unit 17, which is located on the back structure and receives the rotation angle signal from the angle sensor 13 and the control command to control the drive motor, the pawl, and the ratchet module 14. The main controller adjusts the upper limb exoskeleton's system stiffness and damping parameters in real time based on an admittance model, reducing the risk of user injury due to component failure.

This invention utilizes a drive motor-series elastic actuator (SEA) and drive cable transmission design to provide upper limb assistance. A ratchet brake module (pawl and ratchet) is located between the drive motor and the SEA, locking the drive cable in an emergency. Combined with the invention's control interface (human-friendly voice interface), the user simply presses a button, taps the touchscreen, or uses a voice command to stop the exoskeleton. The pawl and ratchet lock the drive cable, and the drive motor enters a power-saving standby mode, conserving battery power. At this point, the exoskeleton still provides basic assist and cushioning functions through the series-connected elastic actuators and torsion springs at the elbow joint, allowing the user to complete the current action, such as putting down a heavy object, and then resolve the cause of the emergency, such as leaving a dangerous area or troubleshooting a malfunction in the exoskeleton's drive motor. The user can also trigger the exoskeleton's safe operating mode using voice commands or buttons on the wearable interface. This allows the upper limb exoskeleton device to adjust system stiffness and damping parameters in real time based on the current operating conditions, reducing the risk of injury to the user while optimizing energy efficiency.

In one embodiment of the present invention, one or more single-degree-of-freedom joints and bearings can be provided at the shoulder joint unit to meet the needs of human body movements.

One embodiment of the present invention proposes a user-friendly human-machine interface exoskeleton hardware-software architecture that combines a finite-time convergent reduced-order linear expansion state observer (FRLESO), self-tuning proxy sliding mode control (PSSMC), adaptive admittance control (AAC), a rope-driven series elastic actuator (SEA), a pawl-ratchet brake module, and voice interaction and wearable interfaces. This architecture improves the safety and energy efficiency of active upper-limb exoskeleton systems. First, a mathematical model of a rope-driven active-passive dual-mode upper-limb exoskeleton is derived, and a self-tuning proxy sliding mode control (PSSMC) is designed for the upper-limb exoskeleton to address safety issues. Next, considering the unmeasurability and compliance of partial system states and lumped disturbances, the authors introduce the RLESO and AAC within the proposed PSSMC framework to propose an adaptive admittance surrogate sliding mode control based on a finite-time reduced-order linear expansion state estimator (AAPSMC-FRLESO). AAPSMC-FRLESO treats lumped disturbances as expansion states for estimation and compensation, thereby improving user safety and assisted trajectory tracking performance of upper-limb powered exoskeletons under unknown parameters and time-varying uncertainties. Finally, software and hardware integration is performed. Software is a control technology that balances assistance, compliance, and safety. This addresses safety issues previously associated with active upper-limb exoskeleton control command communication, such as jitter and loss of stability caused by signal dropouts, as well as excessive peaks and oscillations caused by accumulated errors, as shown in Figure 2. Safety is further enhanced through a user-friendly human-machine interface, voice module, wearable interface, and ratchet brake. This reduces the risk of injury to the user due to malfunctioning of the active upper-limb exoskeleton's motor drive circuit module, thus resolving safety issues associated with users' arms being restrained by the upper-limb exoskeleton.

Admittance control controls position based on the magnitude of the human-machine interaction force. Therefore, the human-machine interaction force is the input, and the position is the output. Before discussing admittance control, it is necessary to explore how to obtain the human-machine interaction force. In interaction methods, force signals refer to the force generated by human muscle contraction acting on a mechanical structure. In control systems, this force is referred to as interaction force and can be measured intuitively using force sensors, motor current loops, and other methods. Using force signal measurement not only avoids the inconvenience of applying electromyographic patches to measure biosignals but also allows for more intuitive identification of the wearer's limb movement intent. Therefore, this invention uses force signal measurement as the human-machine interaction force input for admittance control of a powered exoskeleton. Currently, force signal measurement methods include the following. (1) Torque sensor: It has good dynamic performance and mature technology, but its mechanical structure is relatively complex and it is difficult to use in powered exoskeletons with strict volume requirements. (2) Harmonic reducer: This measurement method can achieve the same effect as the torque sensor by measuring the angle difference between the two sides of the harmonic, but its harmonic deformation characteristics are very complex and there are torque fluctuations with a fixed frequency, which makes this type of research very rare. (3) Joint current: This method measures force by obtaining the motor output current and separating the part generated by the exoskeleton joint dynamics to obtain the human-machine interaction force. This method does not require a cycle. Edge sensors have a simple structure and low cost, but are difficult to calculate accurately due to the influence of friction between gears and structures, resulting in low control accuracy; (4) Serial elastic actuator: This measurement method adds an elastic element to the driving end and the load end, and calculates the human-machine interaction force by measuring the deformation of the elastic element. In the application of this invention, a magnetic position encoder is added to the outside of the elastic element to measure the deformation, thereby calculating the human-machine interaction force. The exoskeleton joint constructed in this way is called serial elastic drive, which is also one of the most popular research directions in human control of machines. The purpose of admittance control is to convert force into position. Position control provides the exoskeleton with excellent compliance. This invention employs position-based impedance control, also known as admittance control, to achieve compliance and comfort in human-robot collaboration within the exoskeleton. It also provides an overdamped safety response to large tracking errors, preventing unresolved vibrations caused by external forces that could lead to danger or injury.

Admittance control can be categorized as fixed-parameter admittance control and variable-parameter admittance control, depending on whether the model parameters automatically change during the control process. Fixed-parameter admittance models require manual adjustment to achieve appropriate compliance, which is more cumbersome. Variable admittance models automatically adjust compliance based on actual needs by varying the admittance parameters. Previous research has shown that for good tracking performance, high damping and low speed are required for precise movement. Conversely, for large-scale movement, low damping is required for rapid motion. Because of these individual factors, the relationship between the wearer's operating force and output speed is subject to dynamic change. Therefore, the compliance control of the powered exoskeleton must meet the following requirements: (1) motion accuracy at low speeds; (2) full-range human-machine interaction force stability; and (3) sensitive high-low speed switching capabilities. To this end, the present invention adopts an adaptive admittance control strategy to optimize the compliance of human-machine interaction. The powered exoskeleton requires human-machine interaction with the arm during the power assistance process. The use of FRLESO-PSSMC can ensure the safety of the use process. However, when it comes to contact with the human body, admittance control is generally used as a compliance strategy. Admittance control is a force-based compliance control strategy that can achieve the purpose of compliance control by establishing a relationship with position. Therefore, this invention introduces adaptive admittance control based on the FRLESO-PSSMC to overcome the rigid limitations of traditional impedance control. Admittance control involves inputting the measured human-machine interaction force into an admittance model to obtain an angle correction for the tracking trajectory. This correction then adjusts the preset tracking trajectory of the joint to improve the compliance and comfort of human-machine interaction. Designed for exoskeleton systems, the AAPSMC-FRLESO of this invention ensures the safety of power assistance and the tracking performance of the power trajectory under conditions of unknown parameters and uncertainty, while also meeting the requirements for individualized wearability.

The admittance model commonly used by collaborative robotic arms is as follows:

Where Vθ ( s ) is the angular velocity, FI ( s ) is _the human-machine interaction force, and I , B , and K are the equivalent inertia, damping, and stiffness of the system, _respectively . Because the upper limb powered exoskeleton controlled by the present invention has a relatively small acceleration change during the process of lifting or carrying heavy objects with joint assistance, the admittance model used in the present invention ignores the inertia parameter in equation (1) and simplifies the admittance model to:

From equation (2), we can further obtain the relationship between the human-computer interaction force and the tracking trajectory correction value △θ:

Fixed-parameter admittance models cannot adapt to the individual differences of different wearers and adjust the compliance of powered exoskeleton systems in real time. Furthermore, model parameters must be manually adjusted to achieve appropriate compliance based on the assistance requirements of different scenarios. Previous research has shown that when the wearer requires good gait tracking, higher damping and lower speed are required for accurate movement; when the wearer requires a wide range of motion, lower damping is required for rapid movement. Because of these individual differences and the need for exoskeleton compliance and comfort, the relationship between human-machine interaction force and output speed is in a state of dynamic change. Therefore, the present invention adopts an adaptive admittance control method to optimize the human-computer interaction experience. To reduce the computational burden of the control platform, the present invention designs the parameter adjustment law of the exoskeleton admittance model (controlled by the main controller unit) as follows:

in is the stiffness adjustment coefficient, is the damping adjustment coefficient, θ _E (t) is the joint angle measured by the angle sensor, θ _M is the maximum rotation angle of the joint, K ₀ is the stiffness baseline value, B ₀ is the damping baseline value, K(t) is the required stiffness value for the system, and B(t) is the required damping value for the system. When the upper limb follows the exoskeleton's movement, the exoskeleton needs to raise the upper limb to the desired angle. When the difference between the desired angle and the actual angle is large, increasing the admittance stiffness ensures that the output angle compensation is not excessive under large human-machine interaction forces. As the exoskeleton joint gradually raises the joint angle, the required force decreases, and the stiffness variation also decreases.

Thus, this invention provides an upper limb exoskeleton device with safe operation. This invention utilizes safety control technology to address safety issues previously encountered in active upper limb exoskeleton control command communication, such as signal dropouts leading to loss of stability, jitter, and excessive peak vibrations caused by integrated cumulative errors. While also ensuring compliance, this invention also incorporates a user-friendly human-machine interface voice module that locks the ratchet brake, reducing the risk of injury to the wearer due to malfunctions in the active upper limb exoskeleton's motor drive circuit module. It also addresses the battery life issues previously encountered with active upper limb exoskeletons.

The above embodiments are merely illustrative of the features and functions of the present invention and are not intended to limit the scope of the substantive technical content of the present invention. Anyone skilled in the art may modify and alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be as set forth in the patent application described below.

10: Body

11: Back structure

12: Hand structure

12A: Shoulder joint unit

12B: Elbow joint unit

13: Angle sensor

14: Driving motor

141: Series elastic actuator

142: Drive Line

14A: Pawl and ratchet module

15: Power supply unit

16: Control Interface

17: Main controller unit

Claims (9)

An upper limb exoskeleton device with a safe operation function includes: a main body, which is worn on the upper body of a user, and has a back structure and a second hand structure, the second hand structure being respectively arranged on both sides of the back structure, and the second hand structure having a shoulder joint unit and an elbow joint unit; two angle sensors, which are respectively arranged on the shoulder joint unit for sensing the rotation angle of the shoulder joint unit; two drive motors, which are arranged on the back structure and connected to the second hand structure through two series elastic actuators and two drive lines , and drives the shoulder joint unit of the second hand structure to rotate; a control interface, worn by the user, for sending control commands; a power supply unit, for supplying power to the various components of the upper limb exoskeleton device; a main controller unit, located on the back structure, receives the rotation angle signal from the angle sensor and the control command to control the drive motor; the main controller unit adjusts the system stiffness and damping parameters of the upper limb exoskeleton device in real time based on an admittance model to reduce the risk of injury to the user. In the upper limb exoskeleton device with safe operation function as described in claim 1, the drive motor is a brushless DC motor. The upper limb exoskeleton device with a safe operation function as described in claim 1, wherein the elbow joint unit is provided with a torsion spring. The upper limb exoskeleton device with a safe operation function as described in claim 1, wherein the drive motor has a pawl and a ratchet for locking or unlocking the drive line. The upper limb exoskeleton device with safe operation function as described in claim 1, wherein the control interface is a touch controller or a voice controller. The upper limb exoskeleton device with safe operation function as described in claim 1, wherein the main controller unit communicates with the angle sensor and the drive motor via CAN bus. The upper limb exoskeleton device with safe operation function as described in claim 1, wherein information is transmitted between the control interface and the main controller unit via Bluetooth. The upper limb exoskeleton device with safe operation function as described in claim 1, wherein the drive line is a rope, chain, belt or other type of flexible transmission device. In the upper limb exoskeleton device with safe operation function as described in claim 1, the admittance model of the main controller unit is: Where ħ is the stiffness adjustment coefficient, is the damping adjustment coefficient, _θE (t) is the joint angle measured by the angle sensor, _θM is the maximum rotation angle of the joint, _K0 is the stiffness reference value, _B0 is the damping reference value, K(t) is the stiffness value that needs to be increased in the system, and B(t) is the damping value that needs to be increased in the system.