Technical Field

The present invention relates to a robot designed for use in the rehabilitation of extremities.

Background of the Invention

The rehabilitation of extremities in patients after surgery, longer bed rest, or another form of physical inactivity etc. has so far taken the form of physiotherapy, where a physiotherapist has supported the patient during the rehabilitation of relevant extremities. This work often leads to relatively heavy lifting in ergonomically inappropriate working positions that can wear out the employees engaged in this work and also causes the rehabilitation of patients to be far from optimal. Moreover, a physiotherapist is only able to treat one patient at a time. In the following sections, the invention is expounded based on the assumption that extremities are rehabilitated with the involvement of a physiotherapist, yet it must be emphasized that this should not be interpreted in such a way as to limit the use of the robot, as the robot can also be operated by an untrained physiotherapist and used for the rehabilitation of the extremities of animals.

The physiotherapist’s physical rehabilitation work can be done using a robot arm. The robot arm makes the work easier, as it prevents relatively heavy lifting in ergonomically awkward working positions, while permitting the correct repetition of the exercises ordered by the physiotherapist.

A programming unit can be programmed interactively by an operator. The operator programs a rehabilitation motion cycle in the robot arm’s controller by activating, with the extremity connected to the robot arm, the programming key and executing the rehabilitation motion cycle relevant to the extremity of the respective patient once. The operator then deactivates the programming key and activates a "learning function", whereby the relevant rehabilitation motion cycle is carried out an appropriate number of times or, alternatively, for a suitable period of time, after which the motion cycle of the robot arm is set.

The solution is excellent insofar as repetition of ordered exercises is concerned, but there seems to be room for improvement or further development, since the robot is designed to react to the smallest resistance to the motion from the patient and abort the motion.

When it comes to further development, it has been discovered that the effect of rehabilitation increases when the patient actively takes part in the exercises rather than passively lets the robot arm perform the ordered rehabilitation movements. The present invention therefore relates to and describes embodiments of the robot arm, where the training motion is of a more interactive nature and the patient can take active part in the performance of the ordered exercises.

More specifically, the robot is designed to record a motion that is guided by an authorized person, e.g., a physiotherapist, where, as a first dataset, a motion is saved in the robot’s memory, which is described with three-dimensional coordinates for a number of points that plot the position of the robot arm during the course of the guided motion. The movement can subsequently be defined as a trip between two successive coordinates that can take place across the entire dataset of three-dimensional coordinates. The number of coordinates can be configured with an eye to making it possible to repeat, with reasonable accuracy, the motion guided by the authorized person. For example, the objective could be to repeat the motion with an accuracy of 1 cm from the motion guided by the authorized person, which can limit the number of coordinates. The number must be chosen with due regard for the requirement for accuracy and the computing power that is available for calculating the path between the coordinates if the path has to be described by means of interpolation between two successive coordinates. Such a path described with a dataset of three-dimensional coordinates will also hereinafter be referred to as the "trajectory." In one embodiment, the number of coordinates can be determined with an eye to an adjustable repeat accuracy of the motion in the interval of 0.1 to 30 mm. This is calculated when sampling rate is selected, for example, 100 ms. This will result in reasonable repetition of the exercises for as much effect from the training as possible.

In one embodiment of the robot, the robot arm is fitted with various sensors connected to the control unit. Quite specifically, the sensors can be force sensors for measuring the forces that the robot applies or is exposed to. Moreover, the robot arm in one embodiment is fitted with motion sensors in the form of at least one accelerometer for measuring the robot arm’s movement, including speed, acceleration, and direction. In one embodiment, the robot arm is fitted with at least one sensor in the form of a gyroscope for measuring the angle of the robot arm relative to the base.

In its simplest form, after the recording of the motion guided and recorded by the physiotherapist, the robot is designed to repeat the motion as a guided motion for the patient. The patient here is passive, while the robot is active and carries out the mechanical movement that constitutes the exercise motion. Once completed, this motion can be repeated. The robot appropriately moves the position back to the start point of the exercise so a new motion can begin. Since the robot is still connected to the limb, this motion must also be made in a way that takes due account of the connected limb so as to prevent any harm to it. The motion is repeated by processing the data of the coordinates described in the dataset that constitute the trajectory and recreating, based on this data, a trajectory motion with the desired accuracy as input for the robot arm to initiate and perform a movement.

In one embodiment, the robot is designed to monitor a motion that constitutes a movement of the robot arm from one point to another with the recording of another dataset that includes three-dimensional coordinates for position, parameters for force measured by at least one force sensor, speed, and direction of movement, as measured by at least one accelerometer. The dataset that is recorded when an external force, for example, the patient, actively performs exercises is thereby extended with values that describe the force the patient exerts towards the robot.

In one embodiment, the robot is designed to compare the second dataset with the first dataset, which constitutes the trajectory, and calculate the deviation in position.

In one embodiment, the robot is configured to create a third dataset, which has, as its first parameter, the trajectory, with three-dimensional coordinates in point form, and, as its second parameter, a value in the form of an adjustable threshold range around the trajectory. This way, a space is defined around the trajectory that can be used as a tolerance margin before activating a function or as an area where the robot is required to perform a certain function that can be active or passive. As a visual explanation, it can be imagined as a three-dimensional tube formed around the trajectory that describes a threshold value for deviations from the trajectory.

In one embodiment, the robot is designed to compare the trajectory with the third dataset and calculate the deviation in force, movement, and position.

In one embodiment, the third dataset contains several coordinated values that describe parameters for distance from the recorded motion. Distance from a center point is thus described as distance rings on a target, but here the form is spherical, as it is the distance from the center point that determines whether a position is inside this area. Here it must be kept in mind that a high sample rate will generate closely spaced center points that describe the curve, which is why there can be an overlap.

In one embodiment, the robot is configured to change function in response to the amount of deviation from the trajectory. The function change further depends on monitored values from sensors. Thus, an active motion by the robot can be terminated if the robot arm is subjected to a force that exceeds a threshold value, if the robot arm is put outside the threshold value of a position, or if the robot arm is moved with a speed or acceleration that exceeds a threshold value. The threshold value is, as mentioned before, configured in the third dataset.

In one embodiment, the robot is designed to monitor a passive motion, where an external source, for example, a patient must try to repeat a movement that describes the trajectory. In one embodiment, the robot is designed to change, in case of deviation from the trajectory within the threshold values described in the third dataset, its function to active motion, where the robot, with a force defined in the third dataset, attempts to guide the movement back to the trajectory motion. The magnitude of the force can be variable as a function of the magnitude of the deviation, or it can be a fixed value determined once a number of threshold values that define a distance from the trajectory are exceeded.

In one embodiment, the robot arm is designed to continuously calculate where the nearest point on the trajectory is in relation to the current motion in order to calculate the deviation in distance and direction with an eye to providing input for calculating the desired response from the robot arm for trying to guide the movement back to trajectory motion.

In one embodiment, the robot is designed to monitor a passive motion and, when a position value that is within an area determined by the trajectory and a threshold value for deviation is reached, to change function from passive to active, where the robot exerts resistance against the force exerted externally, e.g., by a patient, for achieving a greater rehabilitation effect. The function is ideal when the robot must make sure that, for example, a knee is not overloaded, but resistance is only exerted when the knee is sufficiently extended.

In yet another embodiment, the robot is designed to repeat the motion as a passive motion, where the robot monitors the movement exerted by an external source, for example, a patient during a movement and the forces exerted during the movement. Here the robot arm is passive, as it does not actively guide the object. It instead monitors the movement that is exerted by an external source such as, e.g., a patient, including the course of the movement and which forces the external force, for example, the patient triggers during the movement.

In one embodiment, the robot is designed to monitor an active motion from an external source, for example, the patient, and, depending on the magnitude of the deviation in position from the trajectory based on predefined values for force, to calculate a value for force and direction that the robot arm must provide in order to guide the motion back to the trajectory motion.

In one embodiment, the robot is designed to exert resistance to a movement that is applied by an external source, for example, a patient who performs an exercise. The resistance exerted by the robot to the movement in one embodiment is a fixed value over the entire movement sequence.

In one embodiment, the robot is designed to change the resistance exerted to the movement in accordance with a parameter that is linked to the dataset and refers to the coordinates in the reference dataset.

In one embodiment, the robot is designed to permit the resistance that is exerted to the movement rise from one level to another level from the beginning to the end of the movement.

In a preferred embodiment of the robot, the robot arm is further fitted with various sensors connected to the controller in the console that ensure that the relevant exercise motion cycle stops at once if there is resistance in the robot arm that exceeds a predefined force value. This can, for example, be a pain response from the patient that causes the patient to react by "jerking" the limb that is being rehabilitated.

In the following sections, the invention is described in detail with reference to the drawing, where:

fig. 1 is a perspective view of a robot for rehabilitation of extremities in accordance with the invention, fig. 2 is a view showing a connection to the robot arm in the form of a fixture, where the fixture is designed to hold an extremity, here a leg,

fig. 3 is a view showing a movement where the patient is passive and the robot is active, and fig. 4 is a view showing a movement where the patient is active, while the robot monitors the motion and acts passively or actively depending on the patient’s accuracy in repeating the motion in relation to the trajectory.

Fig. 1 shows a perspective view of a robot 2 for rehabilitation of extremities in accordance with the invention. The robot 2 comprises an articulated robot arm 4, which is anchored to a console 6 comprising a controller and a programming unit, and a base 8, that is positioned movably on four swivel wheels placed at the corners of base 8. The base in the displayed embodiment is approximately U-shaped, where the console is anchored to the bottom of the U-shaped base and has legs projecting from it forward in the direction of the robot arm 4, on the front 10 of the robot 2. The robot arm 4 further comprises a head 14, to which a linkage 16 is connected. The linkage 16 further comprises a release key 17 that permits motion of the robot arm 4 to a desired position and a programming key 18 for interactive programming of the programming unit of the controller in console 6. The console 6 further comprises a control panel 20 and buttons 22 for service of the robot 2. The back 12 of the robot is further fitted with an emergency stop 24 and a maneuvering bracket 38 for maneuvering the robot 2 so that it can be placed in a preferred position with respect to the treatment of a given extremity (not shown).

Fig. 2 shows a perspective view, where the robot arm is used, with a fixture 106, as a link between the robot arm 4 and a current extremity, here shown in the form of a leg. The robot arm is thus connected to the extremity and can perform an exercise motion based on a programmed motion. Here the patient can be passive when the robot arm is active, or the patient can be active when the robot arm is passive and monitors the motion, indicating the deviation with which the patient repeats the training exercise. The robot arm can also be designed to monitor an exercise where the patient is active and repeats a training exercise and then change the setting from passive to active if the patient’s motion deviates from the desired programmed motion and thereby actively moves the arm so that the motion of the training exercise follows the programmed motion.

For an explanation of an exercise motion where the patient is passive and the robot arm is active, see the path in fig. 3 that shows the exercise motion. In this function, it is therefore the robot arm that exerts force and moves along the desired course. It must be noted that the path does not show the course of the exercise in 3D. The path between the two points, "start point" and "end point", therefore indicates the path of an exercise from beginning to end, where the movement passes through points in the form of coordinates saved in the memory of the control unit. The path can thus excellently describe a curved shape that constitutes an exercise ordered by a physiotherapist. The path can be handed in as data or recorded by the physiotherapist by moving the extremity while it is connected to the robot arm along a path that constitutes a programming or "learning mode". As is evident from fig. 3, the robot is designed to measure the force of the resistance to the robot arm’s movement and, if the force exceeds a programmed limit, to react by aborting the movement. To achieve repetition of the exercise movement, the robot arm can be configured to guide the robot arm back to the "start point" when the "end point" is reached. This movement will, as appropriate, also be programmed or will be realized along the coordinates of the first movement, between the "start point" and "end point", but in reverse order. It other words, attention must be paid to ensuring that the movement of the connected limb is realized in a way that does not injure or cause pain to the patient.

Fig. 4 shows an exercise motion where the patient is active and carries out an exercise, whereas the robot arm is, in part, passive when it comes to exercising force and, in part, monitors the course of the exercise and indicates if it proceeds according to the desired sequence determined by the

physiotherapist and programmed as a reference dataset or the "trajectory." The indication can be visual, where the patient, with arrows on a screen or similar, is informed if the exercise is performed correctly or needs to be corrected. In yet another mode, the robot arm is, as indicated by fig. 4, equipped with programmed limit values for deviation of the exercise motion performed by the patient before the robot arm changes function from passive to active and tries to change the course of the exercise back to the "trajectory" by force. The exerted forces, which are illustrated with arrows facing towards the center line, can change their strength depending on how much the movement deviates from the trajectory, but can also be set as a fixed value. The robot arm can change function from active to passive when the "trajectory" or border area surrounding it is reached and will remain passive until a new deviation beyond a limit value is recorded. The return motion from "end point" to "start point" can be realized by the patient by exercising force. The robot arm can also be configured to actively make the motion back to the "start point", while taking due account of the connected limb, so as not to injure or cause pain to the patient. The robot arm can appropriately follow the same path back from "end point" to "start point" as from "start point" to "end point" by using the same coordinates for the course of the path so that the return path follows the same course along the same coordinates in both directions. On the return path, the robot arm can also be configured to be passive, while the patient actively guides the limb back to the "start point", but it can actively intervene and guide the movement if it is outside the "trajectory", with an appropriate tolerance, or, if the movement is not carried out with an appropriate speed, it can intervene and apply force that ensures the right speed for the motion.

List of referral numbers:

2 robot

4 robot arm

6 console for robot with controller and programming unit 8 base

10 front of robot

12 back of robot

14 head of robot arm

16 connection unit for connection to extremity

18 programming keys for inactive programming of robot

20 control panel for robot

22 button on control panel

24 emergency stop

38 maneuvering bracket on console 6

106 fixture