ROBOTIC PLATFORM FOR HIPPOTHERAPY AND METHOD FOR MOTOR AND COGNITIVE ASSESSMENT AND STIMULATION

Abstract

A cognitive assessment and stimulation method and a robotic platform for hippotherapy that comprises a structure comprising at least a high torque servomotor, and an articulated mechanism that simulates the horse's head, at least two load cells placed on the articulated mechanism of the structure, for controlling direction and speed, at least one seat module, that comprises at least one inertial sensor of posture intended to be placed on the patient to determine his/her posture, and one or more load cells placed on the seat to determine the load distribution thereon; and at least two pressure sensors for speed control and that further comprises a temperature control module, which allows temperature control, a visual stimulation sub-module and/or an auditory stimulation sub-module, a crane type module coupled to a harness comprising some stirrups which allow the transfer of the patient and also providing control of weight on the platform and give security to the patient, avoiding the risk of falling.

Claims

1. A robotic platform for hippotherapy, comprising: a structure comprising at least one high torque servomotor, and an articulated mechanism simulating the head of a horse, at least two load cells located in the articulated mechanism of the structure, for the control of direction and speed, at least one seat module, comprising at least one inertial sensor of posture intended to be placed on the patient to determine his/her posture, and one or more load cells located in the seat to determine the load distribution thereon; and at least two pressure sensors for the control of speed.

2. The platform of claim 1, further comprising a temperature control module, with one or more temperature sensors, and that allows temperature control.

3. The platform of claim 2, wherein the temperature control module comprises a coating of a nichrome wire frame coated with silicone, controlled by a solid state relay and a microcontroller with a proportional, integral and derivative (PID) control based on an internal control model (ICM).

4. The platform of claim 1, further comprising a crane module intended to be connected to the patient via a harness and some stirrups to reduce his/her weight on the seat module and correct the position thereof.

5. The platform of claim 1, wherein the at least one seat module comprises a plurality of inertial sensors intended to be placed on the head, the cervical vertebrae, the lumbar vertebrae and on the hip of the patient, in order to examine the lateral movement of the whole trunk segment.

6. The platform of claim 1, wherein the at least one seat module comprises at least three load cells to determine the patient's location, the total weight of the patient and a strength vector.

7. The platform of claim 1, wherein the seat module also comprises a visual stimulation sub-module connected to the load cells in order to indicate the position of the patient and a correction of patient's body location by visual stimuli.

8. The platform of claim 7, wherein the visual stimulation sub-module comprises a RGB LED ring indicating weight distribution via colors in a direction in which the patient's body is located.

9. The platform of claim 7, wherein the visual stimulation sub-module comprises a screen with color sequences indicating the weight distribution.

10. The platform of claim 1 wherein the seat module also comprises an auditory stimulation sub-module that comprises a player and a speaker to indicate corrective actions to the patient.

11. The platform of claim 1, further comprising a processing module connected with the rest of the platform elements to configure its functioning.

12. The platform of claim 1, further comprising a communication module that connects the processing module with the rest of the elements of the platform.

13. A method for cognitive assessment and stimulation, comprising: defining a set of functioning parameters of a robotic platform; initiating a movement on the robotic platform; via at least one servomotor; receiving a control signal from the patient, via pressure sensors or load cells placed on an articulated mechanism of the structure; determining the direction and speed set by patient based on the received control signal; determining a posture of the patient based on a signal coming from inertial sensors of a seat module; determining a distribution of patient's load on the seat via a signal coming from the load cells placed on a seat; calculating a movement required to correct the patient's posture, via a processing module; physically, visually or auditorily stimulating the patient to correct his/her posture, via a crane module, a visual stimulation module and/or an auditory stimulation module.

14. The method of claim 13, further comprising a step of controlling a temperature on the seat module via a temperature control module by setting a temperature between 38° C. and 42° C., and variable to simulate heat transfer from a body of a horse.

Description

DESCRIPTION OF THE DRAWINGS

[0060] In order to complete the description being embodied and with the object of helping to a better understanding of the features of the invention, according to a preferable embodiment example thereof, a set of drawings is included as part of said description, which are for illustrative and not limiting purposes, as follows:

[0061] FIG. 1.—depicts a scheme of the coordinates of a Gough-Stewart platform.

[0062] FIG. 2.—depicts the placement of inertial sensors on the body of a patient in an embodiment of the invention.

[0063] FIG. 3.—depicts three load cells that allow to determine the location of the patient on the seat module in an embodiment of the invention.

[0064] FIG. 4.—depicts a scheme of a preferred embodiment of the platform of the invention.

[0065] FIG. 5.—depicts a second view of a preferred embodiment of the platform of the invention that incorporates the temperature control module.

[0066] FIG. 6.—depicts a view of the articulated mechanism that simulates the neck and head of the horse in an embodiment of the invention.

[0067] FIG. 7.—depicts a view of the visual and auditory stimulation module in an embodiment of the invention.

[0068] FIG. 8.—depicts a view of the crane module with harness and stirrups in an embodiment of the invention.

PREFERRED EMBODIMENT OF INVENTION

[0069] The invention is a robotic platform to imitate hippotherapy and which is able to detect the patient's posture through load distribution and reduce body weight.

[0070] The robotic platform for hippotherapy of the invention comprises, in a particular embodiment, a structure (1) with 8 high torque servomotors (2) ASMB04B with a direct current working voltage 11-24V, a maximum torque of 380 kg*cm and a maximum rotation angle of 300° (±150° or from 0° to −300°).

[0071] The platform also comprises an articulated mechanism (3) that simulates the head of the horse, at least two load cells (4) located in the articulated mechanism (3) of the structure (1), for the control of direction and speed, and at least two pressure sensors (11) for the control of speed.

[0072] The platform comprises at least one seat module (5), comprising inertial sensors (6) MPU6050-GY521 of posture intended to be placed on the patient, to determine his/her posture. Sensors (6) MPU6050-GY521 are an inertial measuring unit (IMU) of six degrees of freedom (6DOF), combining a 3-axis accelerometer and a 3-axis gyroscope.

[0073] This sensor (6) plays an important role since, in addition to monitoring the patient's posture, it allows to record the seat orientation.

[0074] The platform also comprises one or more load cells (7) located on the seat (5) to determine the load distribution thereon, which consist of strain gauges, that at the slightest change of strain in the resistance submitted to strains along with a HX 711 module converts the analog signal into a digital signal proportional to the cell deformation (7).

[0075] As shown in FIG. 5, the platform also comprises a temperature control module (10) which allows to control the temperature, that comprises a coating (12) of a nichrome wire frame coated with silicone, controlled by a solid state relay and a microcontroller with a proportional, integral and derivative (PID) control based on an internal control model (ICM). The temperature module has 2 different temperature sensors (9) in charge of obtaining the temperature of modes that emulate a horse in a resting, walking and trotting position, with temperatures from 38 to 42° C., respectively.

[0076] One of the sensors (11) along with a Solid State Relay, are in charge, by means of a proportional integral (PI) system, of controlling the heat generating system, transported by a nichrome string coated with silicone capable of withstanding temperatures of up to 55° C.

[0077] The platform also comprises a processing module connected to the rest of the platform elements to configure its functioning. The processing module is an Arduino One and Mega 2560-type module, and is used for processing mathematic equations and creating tridimensional movements on the Stewart platform, the movement of the articulated movement (3) that simulates the head and neck, the temperature control processing, the data collection from inertial sensors (6) MPU6050, the RGB LED ring control (15) and the control of load cells (7) and the orders from the pressure sensors (11) (FSR402).

[0078] The platform comprises a communication module that connects the processing module with the rest of the elements of the platform. Communication is possible via SPI as well as via the 12C bus, using a multiplexor 12C, therefore it is easy to obtain the measured data.

[0079] The platform has two power sources S-400 of 24 volts and 16.6 amperes each.

[0080] The platform is developed using the solution to the mathematic problem of a Gough-Stewart platform. Thus, real structure data (1) are calculated and implemented in an algorithm in charge of the mobility of servomotors (2). FIG. 1 depicts the coordinates of a Stewart platform, between a base (bottom) and a platform (top).

[0081] By using this approach, 40 possible solutions were found, even though in practice many of the solutions would not be useful, and therefore it was decided to select rotating servomotors (2) instead of linear ones, to reduce the complexity of implementation.

[0082] The servomotors (2) allow for the incorporation of the 3 movements of different planes in one, being the therapist the one who decides how many degrees of yaw, pitch and roll or how much distance in x, y, z the patient needs in the current state of his/her examination together with the 3 intensity levels (walking, trotting and galloping).

[0083] In traditional hippotherapy, the horse should meet certain requirements such as its walk, size, height, temperature and age, while the use of a Stewart platform solves these requirements with a standard model based on mathematic and programming solutions. In traditional hippotherapy, the ground also has a strong influence because it should be flat, instead, as regards the structure, there is no need for an off-site clinic environment.

[0084] The platform is designed with an Arduino microcontroller, which offers the therapist a menu with which he should enter the corresponding values in position of x, y, z and the rotation angles of axes x, y, z (yaw, pitch and roll) for the current stage of the patient along with the suitable level of intensity therefore.

[0085] At any moment of the therapy, the therapist is free to change the parameters in order to improve the result reflected on the patient and seek for better results.

[0086] In the implementation of temperature control, once the model is obtained (internal resistance of the nichrome wire) and the controller designed for the platform, it is possible to apply different adjustment methods of the controller, such as the Ziegler Nichols method, the Cohen Coon method or the internal control model (ICM) among others, that are used to meet the requirements of temperature control of the system.

[0087] In order to compensate the controller, gains of each one of control actions should be adjusted in order to obtain an acceptable response of the process variable. Adjustment methods for proportional, integral and derivative controllers determine the adjustment of the system requirements, such as gain, derived time and integral time. In the controller tuning, the process dynamics should be first identified, then the controller tuning method is selected and from this response, the parameters of the controller to be implemented are determined.

[0088] Since there is the mathematical inverse of the operator describing the platform, this inverse is used as the controller and the closed circuit system is stable with this controller. The internal control model has been used as a control strategy that gives excellent results, thanks to its robustness in the presence of disturbances caused in the system.

[0089] The control by the internal model directly depends on the system structure and its mathematical model, this method consists of designing the controller according to the system requirements. In order to apply this adjustment method, the platform should be tested to see how it responds. From this response, the design parameters are chosen, with these parameters, the controller is designed and, finally, this controller is applied to the plant in order to see its response. In this case, the solution is focused on first order models plus delay time.

[0090] In a particular embodiment, the platform comprises a crane module (13), which also comprises a harness (17) adjusted to the patient's body, placing the sensors (6) as shown in FIG. 2 and placing them: one on the head, another one on the cervical vertebrae, another one on the lumbar vertebrae and two on the hip, in order to examine the lateral movement of the whole trunk segment.

[0091] In the determination of the sitting position, in this case, the platform comprises 3 load cells (7) ELN0418 with their respective modules HX711. FIG. 3 shows three load cells (7) that allow for the determination of patient's location on the seat module (5) using the calculation resulting from one load cell and the other.

[0092] The location of patient on the seat (5) of the platform is shown by means of a ring (15) with 24 programmable RGB LEDs, which is powered with 5 volts and is commanded by a PWM signal of the microcontroller, which, depending on the patient's location will light a color in the direction it is placed, therefore informing the patient to correct the location of his/her body on the structure.

[0093] Other two load cells (4) are placed on the articulated mechanism (3) of the structure (1) to instruct the servomotors (2) of head and neck, therefore determining the stop and direction of structure (1). This movement is commanded by a microcontroller ATMEGA16u2, which is in charge of sending the PWM signal to each servomotor (2). In order to increase the structure speed, pressure sensors (11) FSR402 were used.

[0094] As shown in FIG. 7, LED ring (15) used to determine the location of the patient was also programmed to be used in visual stimuli, which function with a serial communication protocol of one line, meaning that each color corresponds to a signal. The auditory stimuli are achieved with an mp3 module and the signal is amplified and reproduced by a speaker.

[0095] FIG. 8 shows an embodiment of the crane module (13) of the platform of the invention, which also comprises a harness (17) to hold patient and two stirrups (8) to hold his/her legs.

[0096] FIG. 4 shows an embodiment of design and implementation of the robotic platform for hippotherapy.

[0097] The movements performed by the platform emulate the therapeutic movements for hippotherapy. Since there are no equations for modeling these movements, the precision with which the platform performed the rotational and translational movements in axes X, Y, Z was established.

TABLE-US-00001 TABLE 1 Distance (cm) Axis Z 0 2 4 6 8 −2 −4 −6 −8 X 4.1 2.3 1.6 4.0 2.2 2.0 3.3 2.0 4.1 (error %) Y 2.3 0.7 2.3 2.0 2.9 1.9 2.5 1.8 2.3 (error %) Z 5.2 1.7 4.5 4.7 1.4 3.7 0.6 1.5 5.2 (error %)

[0098] Table 1 shows the error percentages regarding the 3 platform axes, being these error percentages lower than 5%, this is, compared with the low repeatability that may be achieved with a horse, a satisfactory result. These results were obtained using distance sensors located on the platform and performing different positions shown in table 1.

TABLE-US-00002 TABLE 2 Angle (degrees) Axis Min (error %) Max (error %) X (error %) −5° (9.4)  7° (8.7) Y (error %) −10° (5.3)  10° (7.6) Z (error %) −20° (11.2) 20° (9.8)

[0099] Table 2 shows the error percentages obtained for minimum and maximum rotational movements for the three axes, the reading of the angle was obtained by acquiring an inertial sensor MPU6050 which is integrated to the platform.

[0100] The temperature control was implemented in an Arduino microcontroller based on PID control (Proportional, Integral and Derivative Controller). This is a feedback controller, which calculates the deviation or error between a mean value and the desired value. The actuator is a solid state relay, which switches a load through a PWM (pulse width modulation) activation signal generated from Arduino. The temperature sensor used was DS18B20.

TABLE-US-00003 TABLE 3 Temperature (° C.) Time (Seconds) 29.3 122 33.6 205 37.9 298 42.2 396

[0101] Table 3 shows time and temperature measurement values for the open circuit heat generating system, the heat generating system is excited by a voltage of 4.3 v (DC) of PWM Arduino and reaches the actuator (solid state relay) and heats the electric resistance of 110 v (AC). These data allow for the calculation of the equation of the first order transfer function that is better adapted to the data collected.

[0102] The controller adjustment process may be empirical or by using more elaborated techniques such as the Ziegler Nichols method, the Cohen Coon method or the internal control model (ICM), the PI controller yield rates implemented using the different yield techniques, are shown in table 4.

TABLE-US-00004 TABLE 4 Methods UAE ISE Mp Ts/sec Empiric 222.1535 135.4448 1.2 484 Ziegler Nichols 311.4675 135.4925 1.3 520 Cohen Coon 242.5618 122.3332 1.35 601 ICM 38.6743 39.9203 1.0 360

[0103] The tuning method by internal model is the one showing better results since it shows shorter set-up time, less exceedance, less dynamic error and less absolute error.

[0104] With the development of the platform, a general error rate was found of less than 10% of rotation and translation movements.

[0105] On the other hand, the seat (5) of the platform allows the evaluation and training of the patient's position, since it records the values of strength vector expressed by the angular value and the magnitude of the vector resulting from the strains present in the three load cells (7), located at the base of the seat module (5) and which output is sent and represented by a circular LED array (15).

[0106] The head and neck of the platform may be controlled to emulate the horse's movements, the control of the head rotation is achieved by the variation of two load cells (4) connected to reins, to apply more stress on one side than on the other, the platform turns the head, as shown in FIG. 6. When the pressure sensors (11) FSR402 are pressed, the system increases speed and when the same tension is applied to both sides of the reins, the system reduces the speed.

[0107] The proposed system has 3 functionalities, a motor function that works performing soft movements to stimulate the lumbar zone and hip; a cognitive function, that stimulates the patient to interact with his/her own hands through auditory and visual stimuli, and a motor and cognitive function which brings together all the capabilities offered by the platform, leading the patient to directly interact with the platform, being him/herself who makes the structure move always under safe conditions.