Robotic system for gait rehabilitation training on various types of walking terrain

Abstract

The present invention relates to a robotic system for gait rehabilitation training that simulates various types of walking terrain for patients with gait deficits. The system comprises a ground walking platform (200) with footplates that are in permanent contact with the user's foot and simulate the reaction forces of walking on a virtual ground. The platforms are designed to support high- and low-frequency movements. A movable GWP frame (400) that allows moving the GWP system from one place to another. A full-body acceleration system (300) imitates forces an individual would experience while accelerating. A virtual reality unit renders the simulated virtual reality environment and displays the user's movement. A control unit coordinates the tasks of the various robotic and virtual reality modules to achieve the goal of simulating walking on different terrains such as flat ground, stairs, or a slope and to offer the patient various supportive modes, for example, passive mode, active mode, and assistance as needed.

Description

Technical field to which invention relates

[0001] The present invention relates to a robotic system for gait rehabilitation training that simulates various types of walking terrain for patients with gait deficits.Indication of background art

[0002] Walking ability is one of the substantialfunctions we need in normal living. Unfortunately, some people, especially individuals suffering from neurological disorders such as stroke, spinal cord injury, or traumatic brain injury can lose this ability. To facilitate recovery of walking in these individuals, their rehabilitation involves gait training.

[0003] Gait training involves the implementation of different tasks including enhancing muscle strength, maintaining balance control, providing pelvic control and, more importantly, training the patient to walk on various types of grounds they may face in their daily living activities. Patients are often trained to walk in more actual types of environments to prepare them for getting by in their places of interest, such as school or a work site. The training involves different types of exercises that vary in difficulty, such as walking on uneven ground, climbing stairs, and turning and stumbling. Thus, developing devices for simulating different environments for the patients becomes important.

[0004] A haptic locomotion interface is a device that creates an artificial sensation of physical walking. Pioneering work in the development of locomotion interface devices began in 1988, and many different prototypes have been fabricated. These robots can be broadly divided into two categories: treadmills and footplate devices.

[0005] Treadmill-based mechanisms produce an infinite floor with a belt that brings the user back during the stance phase so that the swing phase of the opposite foot is executed within the workspace of the system. Standard treadmills usually work unidirectionally, and some are equipped with a tilt mechanism that generates positive or negative slopes. Advanced treadmills simulate infinite planar motion in the frontal and lateral directions. These interfaces are based on several parallel treadmills attached to a main belt that drives them in a direction perpendicular to their routing. The major limitation of the treadmill is its inability to simulate uneven surfaces; in addition, the user is restricted to walking on a stiff floor, and the treadmill cannot simulate virtual grounds with haptic material, like walking on ice or sand.

[0006] Footplate devices are more advanced locomotion interfaces. They imply positioning the walker's feet on two programmable or movable platforms and then applying displacement to each foot. Based on the trajectory they generate, two different mechanisms can be distinguished.

[0007] Fixed trajectory: This class groups all the systems where the trajectory is adjusted before starting the exercise. Generally, the trajectory is elliptic and adjusted by changing the size of each member of the crank-rocker mechanism. These systems can simulate only a simple type of ground (flat ground), e.g., GT and ICARE.

[0008] Dynamic trajectory: This class groups all the systems where the trajectory is not predefined. Typically, it can take any shape within limited ranges according to certain directions, e.g., HapticHaker and the G-EO system. This kind of mechanism can theoretically simulate complex grounds such as stairs or slopes rather than just typical flat grounds.

[0009] The inability of such systems to simulate high-frequency movements, however, is one of the key disadvantages of the current dynamic trajectory mechanisms. This is because the majority of these systems contain heavy components, which make it difficult to cancel their inertia and friction forces while simulating the swing phase of walking. As a result, the user may experience resistance when walking, disrupting the simulation process and creating an incorrect impression of a real walk. Additionally, these systems are limited in their ability to provide the required level of mobility and range of motion when walking.

[0010] Along with the aforementioned drawbacks, not all present haptic devices can provide the user with a sense of full-body acceleration. They restrict the walker's body from speeding because they are stationary systems.Technical problem to be solved

[0011] The invention aims to solve the limitations of the aforementioned haptic devices by satisfying all the physical and visual requirements that make the simulation of walking on different grounds as realistic as possible and to offer the patient various supportive modes, for example, passive mode, active mode, and assistance as needed.Disclosure of invention

[0012] The innovation provides two different types of forcesforsimulating the walking process. A ground walking platform (GWP) is deployed to simulate the ground reaction forces between the user's foot and the platform. The GWP falls into the category of haptic interface with dynamic trajectory, in which the user's feet are in permanent contact with the platform footplates. A full-body mechanism is introduced to simulate the acceleration forces applied to the user's body when walking. The visual feedback of the simulated environment is provided through a virtual reality (VR) headset or a screen display.

[0013] The system is designed to provide different types of assistance according to patients' recovery stages. The rehabilitation process can broadly be divided into three stages: preliminary, intermediate, and advanced. According to the patient's recovery stage, the system may provide different types of assistance modes, including passive mode (the system does not assist the patient), active mode (the movements of the patient are fully supported by the system while the user stays passive), and assistance as needed (the system assists the patient only when it detects the patient's inability to continue the movement).

[0014] To provide the patient with the relevant reaction and acceleration forces and the visual feedback corresponding to the type of simulated ground, the system was established with three main parts: a control unit, a hardware unit, and a VR unit. The control unit coordinates the tasks of the different units to simulate the ground reaction forces generated in response to walking on a ground surface with different degrees of hardness (e.g., walking on concrete or mud) and on a ground surface with different gradients (e.g., walkingon a plane ground, walking uphill or walking downhill), and to simulate the acceleration forces of the whole body while displacing. The hardware unit is the mechanical part of the system. It includes two main mechanical parts: a GWP and a full-body acceleration system. The GWP supports each foot while simulating the aforementioned ground reaction forces. The full-body acceleration system simulates the acceleration forces applied to the whole body. The VR unit visualises the environment simulated by the control unit and applied by the hardware unit. Brief description of drawings

[0015] FIG. 1 illustrates an exemplary gait robotic rehabilitation system that is positioned so different types of virtual environments can be simulated to the patient. FIG. 2 illustrates the GWP (200) and its frame (400). FIG. 3 illustrates a detailed view of the frame of the GWP (400). FIG. 4 illustrates a GWP (600) with 18 degrees of freedom (DOF) total for simulating reaction forces resulting from walking on different types of mediums. FIG. 5 illustrates a detail of one side of the GWP (200) for one foot with nine different DOF actuation mechanisms. FIGS. 6a, 6b and 6c illustrate a detailed view of the GWP X-mechanism, Y-mechanism and Z-mechanism design for the X-, Y- and Z-axes DOF, respectively. FIG. 6d illustrates a detailed view of the GWP six-DOF Stewart platform designed for filtering residual and friction forces and for providing rotation movements around the X-, Y- and Z-axes. FIG. 7 illustrates an exemplary full-body acceleration mechanism (500), in which the embodiment is comprised of three main parts: the full-body acceleration mechanism base frame, the GWP supporting frame, and the actuation system. FIGS. 8a and 8b illustrate, respectively, an exemplary implementation of the impedance and admittance controller for the GWP and full-body acceleration system. FIG. 9 illustrates the overall relationship between the different units of the gait robotic rehabilitation system, including the hardware unit, the control unit and the VR unit. Description of at least one way of carrying out the invention

[0016] Preferred embodiments of the present invention are described hereafter concerning the accompanying drawings.

[0017] FIGS. 1 to 10 illustrate some exemplary embodiments and various views of a gait robotic rehabilitation system and numerous components of the robotic system, following at least one embodiment of the present invention. One embodiment of the present invention may include a rehabilitation robotic system that services a patient in a medical rehabilitation facility. The rehabilitation robotic system may serve a patient by simulating various virtual environments that vary in their shapes and stiffness properties. This can include the simulation of a more typical solid, flat ground to a complex one with different degrees of slope and different haptic materials (e.g., water, sand, and ice). The system also provides patients with different rehabilitation assistive modes based on their levels of recovery. Such modes are known to cause neural adaptations leading to regaining motor function. The system can provide full active assistance for patients in their earlier stages of recovery while the patient stays passive. In the mid-level of recovery, where the patients regain a moderate ability to control their movements, the system only assists as needed. At the later stages of recovery, when patients recover a large amount of mobility co ntrol, the system does not assist the patients. An integrated and reconfigurable rehabilitation robot system that allows the implementation of multiple training procedures further enhances the quality of rehabilitation.

[0018] FIG. 1 illustrates an exemplary gait robotic rehabilitation system that is positioned to simulate various types of virtual terrain for the patients while they benefit from various types of assistance. In the embodiment shown (100), the framework includes a GWP (200), a full-body acceleration mechanism (300), and a GWP frame (400). The GWP (200) is responsible mainly for simulating the reaction forces resulting from walking on different types of terrain. The simulated ground is defined by different physical properties. The terrain that can be simulated can have different shapes, such as plane grounds or inclined grounds. The platform can also simulate grounds with different haptic materials (grounds with different damping or stiffness values), such as stiff or soft. The full-body acceleration mechanism (300) is in charge of simulating the forces that result when the user's whole body is moving.

[0019] FIG. 2 illustrates the GWP (200) and its frame (400). The GWP (200) is fixed to a movable frame (400) that allows moving the GWP system from one place to another.

[0020] FIG. 3 illustrates the frame of the GWP, comprised of a frame main part (410) to which the GWP (200) can be fixed and motorised omni-directional wheels (420) that serve to displace the GWP.

[0021] FIG. 4 illustrates the GWP (600) with 18 DOF. The present embodiment displays the X-mechanism (210), Y-mechanism (230), Z-mechanism (250) and a Stewart platform (270).

[0022] FIG. 5 illustrates one side of the GWP (200) for one foot. The present embodiment design employs linear servo motors in the X-direction (510), the direction of normal gait, to achieve acceptable walking speed, includes a linear servo motor in the Y-direction (520), and incorporates a pantograph, or scissor lift, with a linear servo motor to accomplish Z-direction motion (530). These embodiments are made of heavy parts and are designed to simulate low-frequency translation movements. Since they are designed to support translational movements only, we can call them Cartesian mechanisms. It also includes a six-DOF Stewart platform (270), which is a type of light mechanism we use to simulate high-frequency translation movements, compensate for the residual inertia and friction forces of the heavy parts, and simulate rotational movements.

[0023] The movements of the three Cartesian mechanisms (X-mechanism (210), Y-mechanism (230), and Z-mechanism (250) ) are driven by linear motors. A single linear servo motor mechanism comprises the key following components: rails (X-rails (211) , Y-rails (231), and Z-rails (251) ), carriage (X-carriage (212), Y-carriage (232), and Z-carriage (252) ), and a driving system including a motor coil (X-motor coil (214), Y-motorcoil (234), and Z-motorcoil (254) ), and a magnet track (X-magnet track (213), Y-magnet track (233), and magnettrack (253) ). Thecarriage is mounted on the rails via a linear bearing, which allows it to move along the rails. The motor coil propels itself along the magnet track. The motor coil is attached to the carriage. The carriage is led in place by linear bearings with rails secured to the base. The linear servo motor mechanism is equipped with electrical breaks that can be used in passive mode where the system carries the weight of the whole body, with no need to counter the weight using the motor in active mode.

[0024] FIGS. 6a, 6b, 6c, and 6d illustrate the present embodiment design of the GWP (200) with nine DOF for each foot. A linear servo motor mechanism is used to achieve the desired speed and strength required for simulating human gait speed and acceleration that are significantly high along the sagittal plane. FIG. 6a illustrates the embodiment's X-direction (510) linear servo motor mechanism. FIG. 6b illustrates the Y-direction (520) linear servo motor mechanism.

[0025] Each of the X- and Y-mechanisms has two separate linear servo motor mechanisms (one for each foot). Each of the X-linear servo motor mechanisms is mounted on the carriages (232) of the V-mechanism. Each of the linear motor mechanisms of the Y-mechanism has two carriages (232), oneto move the linear servo motorof the X-mechanism of the right foot along the Y, and one to move the linear servo motor of the X-mechanism of the left foot along the Y.

[0026] FIG. 6c illustrates the embodiment's Z-direction (530) pantograph mechanism and its linear servo motor mechanism. The embodiment has two separate linear servo motor mechanisms and two pantograph mechanisms (one for each foot). Each linear motor mechanism of the Z-mechanism is fixed on the top of a carriage (212) from the X-mechanism. Each linear motor mechanism of the Z-mechanism has one carriage (252) on which one of the bottom extremities of the pantograph is mounted. The carriage is driven by a linear motor. The motor coil (254) propels itself along the magnet track (253); the motor coil is attached to the carriage (252).

[0027] The pantograph mechanism is a parallel high-stiffness mechanism, which has the advantageof providing a wide rangeof motion along the Z-direction. A pantograph, or scissor lift, is a type of platform that moves vertically rather than horizontally. It uses linked, folding supports in a criss-cross pattern, of which there are two. Each criss-cross is made of two bars (257) that are connected at their centres of mass with a revolute joint (258). Each criss-cross has four extremities, two at the top and two at the bottom. One of the bottom criss-crossed extremities is connected with revolute joints to the X-carriage (212 ), and the other is connected to the moving carriage (252 ).

[0028] On the top, one of the extremities of the criss-cross pattern is connected to the Stewart platform carriage (255 ) with a revolutejoint, and at the opposite extremity are rollers (256), which are placed at the bottom of the Stewart platform carriage (255) . The rollers (256) guide one of the extremities of the top criss-cross to translate along the bottom of the Stewart platform carriage (255).

[0029] When the distance between the bottom two extremities of the criss-cross mechanism decreases by moving the Z-carriage (252), the cross struts are stretched out, pushing the top platform (the Stewart platform carriage (255) ) upwards. The opposite happens when the distance increases. In this way, the movement along the Z-direction (530) is generated.

[0030] FIG. 6d illustrates the embodiment of the six-DOF Stewart platform mechanism. A Stewart platform is a type of parallel manipulator that uses six prismatic actuators (271) to provide six-DOF motion: forwardbackwards, up-down, left-right, pitch, roll, and yaw. The six-DOF Stewart platform consists of a moving platform (272) and a base platform (273) linked by six prismatic actuators (271) with spherical or universal joints at the base and spherical joints (274) at the moving platform, and an adjustable pedal foot (275) enclosed and fixed on the top of the moving platform. Between the Stewart platform moving platform and pedal foot is an integrated six-axis load cell (276) . The six-axis load cell (276 ) makes use of the foot pedal haptic feedback sensory unit by measuring force and torque. This present embodiment allows the rehabilitation specialist to measure an individual's exerted loads and torques with a six-axis small load cell (276) in six axes for force feedback impedance control.

[0031] The GWP (200) implements a six-DOF Stewart platform to simulate the rotational movements of the user's foot and filter out the residual friction and inertia forces. The pitch, roll, and yaw movements of the platform are used to simulate the rotational movements of the foot. The platform is made of six hydraulic cylinders that can provide a pic power. This advantage allows for translation movements with high acceleration to get rid of the residual inertia and friction forces. The base of the Stewart platform (273) is fixed to the Stewart platform carriage (255).

[0032] The X-mechanism, Y-mechanism, and Z-mechanism of the ground simulation platform are made of heavy parts. These three mechanisms are advantageous for providing a wide range of motion, especially along the X-direction (520) . However, theirdrawbacks can beseen when simulating high-frequency movements. Since their inertia and frictional forces are important, a lag in movements will result. For instance, by simulating quick movements of the foot in free air, the user can feel resistance. Since the Stewart platform is made of light parts and has hydraulic actuators that provide high instantaneous force, it can simulate high-frequency movements well. To summarise, the heavy parts of the ground simulation platform (210, 230, and 250) are used to simulate low-frequency movements and conveniently provide a wide range of motion, while the light parts of the platform (270) are employed to simulate high-frequency movements.

[0033] One of the main sensations we get while walking in the real world concerns the feeling of force resulting from body acceleration. The acceleration forces are applied to the walker's whole body and give the sense that the user is moving. To obtain the same feeling, a full-body acceleration mechanism (300) was developed. The mechanism accelerates the walker in the whole 3D space by accelerating the whole mechanism system GWP (200) on which the user is stepping in the 3D space. This simulation is limited in distance, but this limitation can be overcome by slowly returning the system GWP (200) to the centre point in addition to the rotation that can emulate an acceleration.

[0034] FIG. 7 illustrates an exemplary full-body acceleration mechanism (300), in which the embodiment is comprised of three main parts: the full-body acceleration mechanism base frame (301), the GWP supporting frame (302), and an actuation system (303). The full-body base frame is fixed to the ground through four pillars. The GWP supportingframe is fixed to the GWP system (200) through four pillars. The GWP supporting frame is suspended from the top by a driving mechanism that freely moves the GWP system in 3D space. The driving mechanism is fixed to the full-body base frame.

[0035] The driving system is made of three linear cylinders perpendicular to each other. One cylinder is parallel to the X-axis (510), anotherto the Y-axis (520), and one to the Z-axis (530). One of the extremities of the X- and Y-cylinders is attached to the base frame through spherical joints, and the other extremities are fixed to the Z-cylinder base by spherical joints.

[0036] The GWP (200) aims to simulate walking on different terrains. The simulation provides the subject with a reaction force based on their foot's position in a virtual environment. The position of the robot is ruled by the contact forces between the foot and the platform and the relative position of the foot in the virtual environment. The GWP is controlled using the impedance control.

[0037] The equation that describes the motion of the GWP robot is: B q q ¨ + C q q ˙ q ˙ + F m q ˙ + g q = u − J T q H where q is a vectorof the robot's joint positions, B(q) represents the inertia matrix, C(q,q̇) describing the centrifugal and Coriolis forces, F m describes the friction coefficients of the manipulator, g(q) is the gravity torque, u is the vector torque applied by the robot, J is the Jacobian matrix and H is the contact force exerted by the manipulator's end-effector on the user's foot.

[0038] The vector H can be written as: H = K P x A _ foot + K D x ˙ A _ foot where K P and K D are the stiffness and damping matrix of the environment, respectively. x foot is a six-DOF vector describing the actual position and rotation of the foot while x A_foot is a vector whose elements represent the position and rotation verifying the desired admittance.

[0039] The system can be controlled with two different types of impedance controls, namely the impedance control with force feedback and the admittance control with position feedback. The admittance control with position feedback is based on sensing the interaction force at the contact point between the robot and the user's foot and transforming it into a desired impedance position x A_foot , according to the desired virtual admittance Z A -1< . The relation between the desired impedance position and interaction force H is given by Equation (3). This type of control aims to lead the position error vector x̃ (Equation 4) between foot position x foot and x A_foot to 0 x A _ foot = Z A − 1 H , x ˜ = x foot − x A _ foot .

[0040] The impedance control with force feedback is based on reading the actual position of the foot. It provides the desired force F A (Equation (5)) according to the desired virtual impedance Z A . The objective of this control is to lead the force error vector F̃ (Equation 6) between the foot force applied on the end-effector (interaction force) and the force vector of the desired impedance F A to 0. F A = Z A x A _ foot F A = K P x A . p _ foot + K D x ˙ A . D _ foot

[0041] x A.p_foot and ẋ A.D_foot are vectors whose elements represent, respectively, position / rotation and translation / rotation velocities, verifying the desired stiffness and damping values of the virtual environment. F ˜ = H − F A .

[0042] FIGS. 8a and FIG. 8b illustrate, respectively, an exemplary block diagram of the admittance control with position feedback and the impedance control with force for controlling the GWP.

[0043] This admittance or impedance control does not mean leading the admittance or impedance to zero but imposing a certain value, which is the admittance or impedance of the simulated medium.

[0044] The model structure is divided into four different parts associated with different functions. The hardware unit represents the manipulator with its own control unit that ensures that the output position follows the input command.

[0045] The VR unit uses different haptic materials, the virtual position, and the real position of the footto provide the admittance unit with the desired admittance by adjusting the stiffness and damping gain to fit the selected environment.

[0046] FIG. 9 describes the system's units and shows the relationship among them.

[0047] The ground reaction force can be simulated in three dimensions, more or less. The control system takes a set of measurements from the hardware unit, describing the state of the robot and the physical state of the walker's foot. These state measures can be forces, positions, or angles. Further, the VR unit provides the control unit with a setof information describing the physical state of the virtual avatar that simulates the patient's motions. This set of information includes relative foot position, body position, and features of the ground (slope and hardness).

[0048] Combining these data, the system generates a set of commands for the robot, such as forces, positions, angles, and voltages for the actuators of the hardware unit. The GWP then follows the patient's feet during the swing phase of walking and moves the feet during the standing phase to simulate walking in the virtual environment, while the full-body acceleration system accelerates the user in the real world. At the same time, the system updates the VR state elements such as relative foot position or body position. The VR unit then displays and simulates an environment and an avatar.

Examples

Embodiment Construction

[0016]Preferred embodiments of the present invention are described hereafter concerning the accompanying drawings.

[0017]FIGS. 1 to 10 illustrate some exemplary embodiments and various views of a gait robotic rehabilitation system and numerous components of the robotic system, following at least one embodiment of the present invention. One embodiment of the present invention may include a rehabilitation robotic system that services a patient in a medical rehabilitation facility. The rehabilitation robotic system may serve a patient by simulating various virtual environments that vary in their shapes and stiffness properties. This can include the simulation of a more typical solid, flat ground to a complex one with different degrees of slope and different haptic materials (e.g., water, sand, and ice). The system also provides patients with different rehabilitation assistive modes based on their levels of recovery. Such modes are known to cause neural adaptations leading to regaining m...

Technical field to which invention relates

[0001] The present invention relates to a robotic system for gait rehabilitation training that simulates various types of walking terrain for patients with gait deficits.Indication of background art

[0002] Walking ability is one of the substantialfunctions we need in normal living. Unfortunately, some people, especially individuals suffering from neurological disorders such as stroke, spinal cord injury, or traumatic brain injury can lose this ability. To facilitate recovery of walking in these individuals, their rehabilitation involves gait training.

[0003] Gait training involves the implementation of different tasks including enhancing muscle strength, maintaining balance control, providing pelvic control and, more importantly, training the patient to walk on various types of grounds they may face in their daily living activities. Patients are often trained to walk in more actual types of environments to prepare them for getting by in their places of interest, such as school or a work site. The training involves different types of exercises that vary in difficulty, such as walking on uneven ground, climbing stairs, and turning and stumbling. Thus, developing devices for simulating different environments for the patients becomes important.

[0004] A haptic locomotion interface is a device that creates an artificial sensation of physical walking. Pioneering work in the development of locomotion interface devices began in 1988, and many different prototypes have been fabricated. These robots can be broadly divided into two categories: treadmills and footplate devices.

[0005] Treadmill-based mechanisms produce an infinite floor with a belt that brings the user back during the stance phase so that the swing phase of the opposite foot is executed within the workspace of the system. Standard treadmills usually work unidirectionally, and some are equipped with a tilt mechanism that generates positive or negative slopes. Advanced treadmills simulate infinite planar motion in the frontal and lateral directions. These interfaces are based on several parallel treadmills attached to a main belt that drives them in a direction perpendicular to their routing. The major limitation of the treadmill is its inability to simulate uneven surfaces; in addition, the user is restricted to walking on a stiff floor, and the treadmill cannot simulate virtual grounds with haptic material, like walking on ice or sand.

[0006] Footplate devices are more advanced locomotion interfaces. They imply positioning the walker's feet on two programmable or movable platforms and then applying displacement to each foot. Based on the trajectory they generate, two different mechanisms can be distinguished.

[0007] Fixed trajectory: This class groups all the systems where the trajectory is adjusted before starting the exercise. Generally, the trajectory is elliptic and adjusted by changing the size of each member of the crank-rocker mechanism. These systems can simulate only a simple type of ground (flat ground), e.g., GT and ICARE.

[0008] Dynamic trajectory: This class groups all the systems where the trajectory is not predefined. Typically, it can take any shape within limited ranges according to certain directions, e.g., HapticHaker and the G-EO system. This kind of mechanism can theoretically simulate complex grounds such as stairs or slopes rather than just typical flat grounds.

[0009] The inability of such systems to simulate high-frequency movements, however, is one of the key disadvantages of the current dynamic trajectory mechanisms. This is because the majority of these systems contain heavy components, which make it difficult to cancel their inertia and friction forces while simulating the swing phase of walking. As a result, the user may experience resistance when walking, disrupting the simulation process and creating an incorrect impression of a real walk. Additionally, these systems are limited in their ability to provide the required level of mobility and range of motion when walking.

[0010] Along with the aforementioned drawbacks, not all present haptic devices can provide the user with a sense of full-body acceleration. They restrict the walker's body from speeding because they are stationary systems.Technical problem to be solved

[0011] The invention aims to solve the limitations of the aforementioned haptic devices by satisfying all the physical and visual requirements that make the simulation of walking on different grounds as realistic as possible and to offer the patient various supportive modes, for example, passive mode, active mode, and assistance as needed.Disclosure of invention

[0012] The innovation provides two different types of forcesforsimulating the walking process. A ground walking platform (GWP) is deployed to simulate the ground reaction forces between the user's foot and the platform. The GWP falls into the category of haptic interface with dynamic trajectory, in which the user's feet are in permanent contact with the platform footplates. A full-body mechanism is introduced to simulate the acceleration forces applied to the user's body when walking. The visual feedback of the simulated environment is provided through a virtual reality (VR) headset or a screen display.

[0013] The system is designed to provide different types of assistance according to patients' recovery stages. The rehabilitation process can broadly be divided into three stages: preliminary, intermediate, and advanced. According to the patient's recovery stage, the system may provide different types of assistance modes, including passive mode (the system does not assist the patient), active mode (the movements of the patient are fully supported by the system while the user stays passive), and assistance as needed (the system assists the patient only when it detects the patient's inability to continue the movement).

[0014] To provide the patient with the relevant reaction and acceleration forces and the visual feedback corresponding to the type of simulated ground, the system was established with three main parts: a control unit, a hardware unit, and a VR unit. The control unit coordinates the tasks of the different units to simulate the ground reaction forces generated in response to walking on a ground surface with different degrees of hardness (e.g., walking on concrete or mud) and on a ground surface with different gradients (e.g., walkingon a plane ground, walking uphill or walking downhill), and to simulate the acceleration forces of the whole body while displacing. The hardware unit is the mechanical part of the system. It includes two main mechanical parts: a GWP and a full-body acceleration system. The GWP supports each foot while simulating the aforementioned ground reaction forces. The full-body acceleration system simulates the acceleration forces applied to the whole body. The VR unit visualises the environment simulated by the control unit and applied by the hardware unit. Brief description of drawings

[0015] FIG. 1 illustrates an exemplary gait robotic rehabilitation system that is positioned so different types of virtual environments can be simulated to the patient. FIG. 2 illustrates the GWP (200) and its frame (400). FIG. 3 illustrates a detailed view of the frame of the GWP (400). FIG. 4 illustrates a GWP (600) with 18 degrees of freedom (DOF) total for simulating reaction forces resulting from walking on different types of mediums. FIG. 5 illustrates a detail of one side of the GWP (200) for one foot with nine different DOF actuation mechanisms. FIGS. 6a, 6b and 6c illustrate a detailed view of the GWP X-mechanism, Y-mechanism and Z-mechanism design for the X-, Y- and Z-axes DOF, respectively. FIG. 6d illustrates a detailed view of the GWP six-DOF Stewart platform designed for filtering residual and friction forces and for providing rotation movements around the X-, Y- and Z-axes. FIG. 7 illustrates an exemplary full-body acceleration mechanism (500), in which the embodiment is comprised of three main parts: the full-body acceleration mechanism base frame, the GWP supporting frame, and the actuation system. FIGS. 8a and 8b illustrate, respectively, an exemplary implementation of the impedance and admittance controller for the GWP and full-body acceleration system. FIG. 9 illustrates the overall relationship between the different units of the gait robotic rehabilitation system, including the hardware unit, the control unit and the VR unit. Description of at least one way of carrying out the invention

[0016] Preferred embodiments of the present invention are described hereafter concerning the accompanying drawings.

[0017] FIGS. 1 to 10 illustrate some exemplary embodiments and various views of a gait robotic rehabilitation system and numerous components of the robotic system, following at least one embodiment of the present invention. One embodiment of the present invention may include a rehabilitation robotic system that services a patient in a medical rehabilitation facility. The rehabilitation robotic system may serve a patient by simulating various virtual environments that vary in their shapes and stiffness properties. This can include the simulation of a more typical solid, flat ground to a complex one with different degrees of slope and different haptic materials (e.g., water, sand, and ice). The system also provides patients with different rehabilitation assistive modes based on their levels of recovery. Such modes are known to cause neural adaptations leading to regaining motor function. The system can provide full active assistance for patients in their earlier stages of recovery while the patient stays passive. In the mid-level of recovery, where the patients regain a moderate ability to control their movements, the system only assists as needed. At the later stages of recovery, when patients recover a large amount of mobility co ntrol, the system does not assist the patients. An integrated and reconfigurable rehabilitation robot system that allows the implementation of multiple training procedures further enhances the quality of rehabilitation.

[0018] FIG. 1 illustrates an exemplary gait robotic rehabilitation system that is positioned to simulate various types of virtual terrain for the patients while they benefit from various types of assistance. In the embodiment shown (100), the framework includes a GWP (200), a full-body acceleration mechanism (300), and a GWP frame (400). The GWP (200) is responsible mainly for simulating the reaction forces resulting from walking on different types of terrain. The simulated ground is defined by different physical properties. The terrain that can be simulated can have different shapes, such as plane grounds or inclined grounds. The platform can also simulate grounds with different haptic materials (grounds with different damping or stiffness values), such as stiff or soft. The full-body acceleration mechanism (300) is in charge of simulating the forces that result when the user's whole body is moving.

[0019] FIG. 2 illustrates the GWP (200) and its frame (400). The GWP (200) is fixed to a movable frame (400) that allows moving the GWP system from one place to another.

[0020] FIG. 3 illustrates the frame of the GWP, comprised of a frame main part (410) to which the GWP (200) can be fixed and motorised omni-directional wheels (420) that serve to displace the GWP.

[0021] FIG. 4 illustrates the GWP (600) with 18 DOF. The present embodiment displays the X-mechanism (210), Y-mechanism (230), Z-mechanism (250) and a Stewart platform (270).

[0022] FIG. 5 illustrates one side of the GWP (200) for one foot. The present embodiment design employs linear servo motors in the X-direction (510), the direction of normal gait, to achieve acceptable walking speed, includes a linear servo motor in the Y-direction (520), and incorporates a pantograph, or scissor lift, with a linear servo motor to accomplish Z-direction motion (530). These embodiments are made of heavy parts and are designed to simulate low-frequency translation movements. Since they are designed to support translational movements only, we can call them Cartesian mechanisms. It also includes a six-DOF Stewart platform (270), which is a type of light mechanism we use to simulate high-frequency translation movements, compensate for the residual inertia and friction forces of the heavy parts, and simulate rotational movements.

[0023] The movements of the three Cartesian mechanisms (X-mechanism (210), Y-mechanism (230), and Z-mechanism (250) ) are driven by linear motors. A single linear servo motor mechanism comprises the key following components: rails (X-rails (211) , Y-rails (231), and Z-rails (251) ), carriage (X-carriage (212), Y-carriage (232), and Z-carriage (252) ), and a driving system including a motor coil (X-motor coil (214), Y-motorcoil (234), and Z-motorcoil (254) ), and a magnet track (X-magnet track (213), Y-magnet track (233), and magnettrack (253) ). Thecarriage is mounted on the rails via a linear bearing, which allows it to move along the rails. The motor coil propels itself along the magnet track. The motor coil is attached to the carriage. The carriage is led in place by linear bearings with rails secured to the base. The linear servo motor mechanism is equipped with electrical breaks that can be used in passive mode where the system carries the weight of the whole body, with no need to counter the weight using the motor in active mode.

[0024] FIGS. 6a, 6b, 6c, and 6d illustrate the present embodiment design of the GWP (200) with nine DOF for each foot. A linear servo motor mechanism is used to achieve the desired speed and strength required for simulating human gait speed and acceleration that are significantly high along the sagittal plane. FIG. 6a illustrates the embodiment's X-direction (510) linear servo motor mechanism. FIG. 6b illustrates the Y-direction (520) linear servo motor mechanism.

[0025] Each of the X- and Y-mechanisms has two separate linear servo motor mechanisms (one for each foot). Each of the X-linear servo motor mechanisms is mounted on the carriages (232) of the V-mechanism. Each of the linear motor mechanisms of the Y-mechanism has two carriages (232), oneto move the linear servo motorof the X-mechanism of the right foot along the Y, and one to move the linear servo motor of the X-mechanism of the left foot along the Y.

[0026] FIG. 6c illustrates the embodiment's Z-direction (530) pantograph mechanism and its linear servo motor mechanism. The embodiment has two separate linear servo motor mechanisms and two pantograph mechanisms (one for each foot). Each linear motor mechanism of the Z-mechanism is fixed on the top of a carriage (212) from the X-mechanism. Each linear motor mechanism of the Z-mechanism has one carriage (252) on which one of the bottom extremities of the pantograph is mounted. The carriage is driven by a linear motor. The motor coil (254) propels itself along the magnet track (253); the motor coil is attached to the carriage (252).

[0027] The pantograph mechanism is a parallel high-stiffness mechanism, which has the advantageof providing a wide rangeof motion along the Z-direction. A pantograph, or scissor lift, is a type of platform that moves vertically rather than horizontally. It uses linked, folding supports in a criss-cross pattern, of which there are two. Each criss-cross is made of two bars (257) that are connected at their centres of mass with a revolute joint (258). Each criss-cross has four extremities, two at the top and two at the bottom. One of the bottom criss-crossed extremities is connected with revolute joints to the X-carriage (212 ), and the other is connected to the moving carriage (252 ).

[0028] On the top, one of the extremities of the criss-cross pattern is connected to the Stewart platform carriage (255 ) with a revolutejoint, and at the opposite extremity are rollers (256), which are placed at the bottom of the Stewart platform carriage (255) . The rollers (256) guide one of the extremities of the top criss-cross to translate along the bottom of the Stewart platform carriage (255).

[0029] When the distance between the bottom two extremities of the criss-cross mechanism decreases by moving the Z-carriage (252), the cross struts are stretched out, pushing the top platform (the Stewart platform carriage (255) ) upwards. The opposite happens when the distance increases. In this way, the movement along the Z-direction (530) is generated.

[0030] FIG. 6d illustrates the embodiment of the six-DOF Stewart platform mechanism. A Stewart platform is a type of parallel manipulator that uses six prismatic actuators (271) to provide six-DOF motion: forwardbackwards, up-down, left-right, pitch, roll, and yaw. The six-DOF Stewart platform consists of a moving platform (272) and a base platform (273) linked by six prismatic actuators (271) with spherical or universal joints at the base and spherical joints (274) at the moving platform, and an adjustable pedal foot (275) enclosed and fixed on the top of the moving platform. Between the Stewart platform moving platform and pedal foot is an integrated six-axis load cell (276) . The six-axis load cell (276 ) makes use of the foot pedal haptic feedback sensory unit by measuring force and torque. This present embodiment allows the rehabilitation specialist to measure an individual's exerted loads and torques with a six-axis small load cell (276) in six axes for force feedback impedance control.

[0031] The GWP (200) implements a six-DOF Stewart platform to simulate the rotational movements of the user's foot and filter out the residual friction and inertia forces. The pitch, roll, and yaw movements of the platform are used to simulate the rotational movements of the foot. The platform is made of six hydraulic cylinders that can provide a pic power. This advantage allows for translation movements with high acceleration to get rid of the residual inertia and friction forces. The base of the Stewart platform (273) is fixed to the Stewart platform carriage (255).

[0032] The X-mechanism, Y-mechanism, and Z-mechanism of the ground simulation platform are made of heavy parts. These three mechanisms are advantageous for providing a wide range of motion, especially along the X-direction (520) . However, theirdrawbacks can beseen when simulating high-frequency movements. Since their inertia and frictional forces are important, a lag in movements will result. For instance, by simulating quick movements of the foot in free air, the user can feel resistance. Since the Stewart platform is made of light parts and has hydraulic actuators that provide high instantaneous force, it can simulate high-frequency movements well. To summarise, the heavy parts of the ground simulation platform (210, 230, and 250) are used to simulate low-frequency movements and conveniently provide a wide range of motion, while the light parts of the platform (270) are employed to simulate high-frequency movements.

[0033] One of the main sensations we get while walking in the real world concerns the feeling of force resulting from body acceleration. The acceleration forces are applied to the walker's whole body and give the sense that the user is moving. To obtain the same feeling, a full-body acceleration mechanism (300) was developed. The mechanism accelerates the walker in the whole 3D space by accelerating the whole mechanism system GWP (200) on which the user is stepping in the 3D space. This simulation is limited in distance, but this limitation can be overcome by slowly returning the system GWP (200) to the centre point in addition to the rotation that can emulate an acceleration.

[0034] FIG. 7 illustrates an exemplary full-body acceleration mechanism (300), in which the embodiment is comprised of three main parts: the full-body acceleration mechanism base frame (301), the GWP supporting frame (302), and an actuation system (303). The full-body base frame is fixed to the ground through four pillars. The GWP supportingframe is fixed to the GWP system (200) through four pillars. The GWP supporting frame is suspended from the top by a driving mechanism that freely moves the GWP system in 3D space. The driving mechanism is fixed to the full-body base frame.

[0035] The driving system is made of three linear cylinders perpendicular to each other. One cylinder is parallel to the X-axis (510), anotherto the Y-axis (520), and one to the Z-axis (530). One of the extremities of the X- and Y-cylinders is attached to the base frame through spherical joints, and the other extremities are fixed to the Z-cylinder base by spherical joints.

[0036] The GWP (200) aims to simulate walking on different terrains. The simulation provides the subject with a reaction force based on their foot's position in a virtual environment. The position of the robot is ruled by the contact forces between the foot and the platform and the relative position of the foot in the virtual environment. The GWP is controlled using the impedance control.

[0037] The equation that describes the motion of the GWP robot is: B q q ¨ + C q q ˙ q ˙ + F m q ˙ + g q = u − J T q H where q is a vectorof the robot's joint positions, B(q) represents the inertia matrix, C(q,q̇) describing the centrifugal and Coriolis forces, F m describes the friction coefficients of the manipulator, g(q) is the gravity torque, u is the vector torque applied by the robot, J is the Jacobian matrix and H is the contact force exerted by the manipulator's end-effector on the user's foot.

[0038] The vector H can be written as: H = K P x A _ foot + K D x ˙ A _ foot where K P and K D are the stiffness and damping matrix of the environment, respectively. x foot is a six-DOF vector describing the actual position and rotation of the foot while x A_foot is a vector whose elements represent the position and rotation verifying the desired admittance.

[0039] The system can be controlled with two different types of impedance controls, namely the impedance control with force feedback and the admittance control with position feedback. The admittance control with position feedback is based on sensing the interaction force at the contact point between the robot and the user's foot and transforming it into a desired impedance position x A_foot , according to the desired virtual admittance Z A -1< . The relation between the desired impedance position and interaction force H is given by Equation (3). This type of control aims to lead the position error vector x̃ (Equation 4) between foot position x foot and x A_foot to 0 x A _ foot = Z A − 1 H , x ˜ = x foot − x A _ foot .

[0040] The impedance control with force feedback is based on reading the actual position of the foot. It provides the desired force F A (Equation (5)) according to the desired virtual impedance Z A . The objective of this control is to lead the force error vector F̃ (Equation 6) between the foot force applied on the end-effector (interaction force) and the force vector of the desired impedance F A to 0. F A = Z A x A _ foot F A = K P x A . p _ foot + K D x ˙ A . D _ foot

[0041] x A.p_foot and ẋ A.D_foot are vectors whose elements represent, respectively, position / rotation and translation / rotation velocities, verifying the desired stiffness and damping values of the virtual environment. F ˜ = H − F A .

[0042] FIGS. 8a and FIG. 8b illustrate, respectively, an exemplary block diagram of the admittance control with position feedback and the impedance control with force for controlling the GWP.

[0043] This admittance or impedance control does not mean leading the admittance or impedance to zero but imposing a certain value, which is the admittance or impedance of the simulated medium.

[0044] The model structure is divided into four different parts associated with different functions. The hardware unit represents the manipulator with its own control unit that ensures that the output position follows the input command.

[0045] The VR unit uses different haptic materials, the virtual position, and the real position of the footto provide the admittance unit with the desired admittance by adjusting the stiffness and damping gain to fit the selected environment.

[0046] FIG. 9 describes the system's units and shows the relationship among them.

[0047] The ground reaction force can be simulated in three dimensions, more or less. The control system takes a set of measurements from the hardware unit, describing the state of the robot and the physical state of the walker's foot. These state measures can be forces, positions, or angles. Further, the VR unit provides the control unit with a setof information describing the physical state of the virtual avatar that simulates the patient's motions. This set of information includes relative foot position, body position, and features of the ground (slope and hardness).

[0048] Combining these data, the system generates a set of commands for the robot, such as forces, positions, angles, and voltages for the actuators of the hardware unit. The GWP then follows the patient's feet during the swing phase of walking and moves the feet during the standing phase to simulate walking in the virtual environment, while the full-body acceleration system accelerates the user in the real world. At the same time, the system updates the VR state elements such as relative foot position or body position. The VR unit then displays and simulates an environment and an avatar.

Examples

Embodiment Construction

[0016]Preferred embodiments of the present invention are described hereafter concerning the accompanying drawings.

[0017]FIGS. 1 to 10 illustrate some exemplary embodiments and various views of a gait robotic rehabilitation system and numerous components of the robotic system, following at least one embodiment of the present invention. One embodiment of the present invention may include a rehabilitation robotic system that services a patient in a medical rehabilitation facility. The rehabilitation robotic system may serve a patient by simulating various virtual environments that vary in their shapes and stiffness properties. This can include the simulation of a more typical solid, flat ground to a complex one with different degrees of slope and different haptic materials (e.g., water, sand, and ice). The system also provides patients with different rehabilitation assistive modes based on their levels of recovery. Such modes are known to cause neural adaptations leading to regaining m...

Claims

1. A gait robotic rehabilitation system comprising: a ground simulation platform to simulate walking on different types of ground (200); a movable GWP frame that allows moving the GWP system from one place to another (400); a full-body acceleration mechanism to provide the user with forces giving the sensation of body acceleration while walking (300); a VR unit to visualise the different types of simulated environments in addition to the movements of the user; a controlling unit to be operable for coordinating the tasks of the different units providing visual and physical feedback responsible for simulating different types of ground and for simulating the acceleration force of the body of the user when walking.

2. The gait rehabilitation system as recited in Claim 1, in which said GWP is a further combination of a low-frequency wide-range movement system ((210), (230), and (250)) and a high-frequency short-range movement system (270).

3. The rehabilitation system as recited in Claim 1, in which said GWP further comprises: a Y-mechanism (230) that is disposed to provide movement along the Y-direction and actuated by a linear actuator, an X-mechanism (210) that is disposed above the Y-mechanism to provide movement along the X-direction and actuated by a linear actuator, a Z-mechanism (250) that is disposed above the X-mechanism to provide movement along the Z-direction and actuated by a linear actuator, a Stewart platform mechanism disposed about the Z-mechanism to provide rotation movements and translation movement for high-frequency.

4. The rehabilitation system as recited in Claim 1, in which said GWP uses sensing interaction force at the contact point between the robot and the users for the admittance control with position feedback.

5. The rehabilitation system as recited in Claim 1, in which said GWP uses sensing foot position for impedance control with force feedback.

6. The rehabilitation system as recited in Claim 1, in which said GWP uses linear motors equipped with electrical breaks that can help in the passive mode.

7. The rehabilitation system as recited in Claim 1, in which said GWP is further configured for various rehabilitation assistive modes, such as passive mode, active mode, and assisted as needed.

8. The rehabilitation system as recited in Claim 1, in which said full-body acceleration mechanism (300) is further comprised of a body base frame (301), GWP supporting frame (302), and actuation system (303).

9. The full-body acceleration mechanism in Claim 6 further hangs the GWP supporting frame from the top by a driving mechanism that freely moves the GWP system (200) on the 3D space.

10. The rehabilitation system as recited in Claim 1, in which said controlling unit is further operable for controlling the GWP, the full-body acceleration, and the virtual environment for proving the relevant visual and physical feedback of the simulated virtual environment.

11. The rehabilitation system as recited in Claim 1, in which said GWP (200) is removable and can be used separately.

12. The rehabilitation system as recited in Claim 1, in which said full-body acceleration (300) mechanism is removable and can be used separately.

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