FR2873017A1 - Myoelectric prosthesis for e.g. arm, has microcontroller to allow prosthesis body movement based on value of voltage created by muscle contraction, and information device to send signal, function of spacing between value and set point - Google Patents

Abstract

The prosthesis has motors (7) to impart movement to a prosthesis body, and sensors (6) to sense a voltage created by the contraction of a muscle of body of a human being. A microcontroller (5) controls the motors to give movement of the body based on the voltage value. Information device sends an information signal, to the human being carrying the prosthesis, which is a function of the spacing between the value and a set point.

Description

2873017 1

  The present invention relates to a prosthesis of a body member of a human being, capable of being moved by humans, for example an arm, hand, elbow or the like prosthesis, using myoelectric technology to control the movement of the prosthesis. This control mode uses the potential difference that is produced by muscle contraction. The muscle cells with anions and cations, a contraction of a healthy muscle (stimuli) results in the displacement of the latter, which causes a potential difference of the order of microvolt. This potential difference is then collected by one or more electrodes disposed on the patient's skin, at the level of the healthy muscle. After possible amplification and analysis by a relay (programmable electronic chip), it is then decided to supply the motor of the prosthesis, for example the arm, the elbow, the wrist or the hand according to the healthy muscle that has been contracted. and the amplitude of the contraction.

  Thus, a prosthesis of this kind comprises a prosthesis body, intended to replace at least part of the limb, a motor mounted to impart a movement to the prosthesis body, at least one voltage sensor to be arranged so to capture a tension created by the contraction of a muscle of the body of the human being; and a control unit that controls the motor to move the body of the prosthesis according to the value of the sensed voltage or a value related thereto.

  These "myoelectric" prostheses of the prior art have in particular the following disadvantage. To make a given movement to the prosthesis, the wearer of the prosthesis must contract a healthy muscle, on which was placed a detection electrode, with a given intensity. Depending on the contracted muscle or the intensity of the contraction, the selected movement (among a set of possible motions pre-recorded in the prosthesis control card) is not the same. If the wearer of the prosthesis fails to achieve a contraction of the muscle that must be contracted to achieve the movement he wants to achieve or if he can not sufficiently control the amplitude of its contraction, the prosthesis does not will not realize the movement that wishes to realize the wearer of the prosthesis.

  But he has no way of understanding his mistake or realizing it. He tries in vain to contract a muscle which he thinks he is contracting at an amplitude which he thinks is good, and nothing happens, or a sudden movement of too great amplitude takes place, or another movement than the one he wishes to take place. To achieve perfect control of his contractions, it takes long months of learning in specialized centers and once returned home, the wearer of the prosthesis has no help. Some days, he manages to achieve the movements he wants and other days nothing works, even though he feels the same contraction as the days when it works. In addition, depending on the outside temperature, the atmospheric pressure and the humidity, the microtension created by the contraction of a muscle is not the same. As a result, these features should also be taken into account when making a contraction to effect movement. Similarly, the mood of the patient is not always the same and it may happen that it is more contracted than other days, more upset than other days, more "electrified" than other days and in In these cases, the contraction to be achieved is not necessarily the same as in the days when it is very calm.

  The present invention aims to overcome the disadvantages mentioned above by proposing a prosthesis of a body member of a human being operating with the myoelectric technology which is easier to use for the wearer of the prosthesis, in particular requires less time for the prosthesis. learning of its use and ensures the possibility of using its prosthesis giving it the movement it wishes to give it with greater regularity over time, including more independently of certain atmospheric conditions or psychological conditions of the body. carrier of the prosthesis.

  According to the invention, the prosthesis as described above is characterized in that an information device is provided for sending an information signal to the human carrying the prosthesis, an information signal which is a function of the deviation or deviations between the detected value (s) of the voltage or voltages or of the value (s) related thereto and one or more setpoints.

  Thus, when the wearer of the prosthesis will achieve a contraction, he will be informed as regards the value of the amplitude of his contraction and in particular whether it is too weak or too large and it will thus be possible for him to modify this contraction depending on the information to make it consistent with its expectations of movement or movement selection. For example, if to flex the left elbow to move the left forearm up and then to the right, the system is pre-registered so that the wearer of the prosthesis must contract, for example, the right thigh. then a contraction of the left thigh, information from the information system about the contraction values detected by the electrodes that will be implanted at his left thigh and right thigh will be sent to the wearer of the prosthesis. If for example he makes a too weak contraction of the right thigh, the information device will inform him. He will be able to correct his contraction until he gets the movement he wants to obtain with a contraction of normal amplitude. Previously, if the system had been set so that the elbow movement would occur only when the amplitude is normal, ie neither too small nor too large, it would not, with a contraction too weak, managed to rotate his forearm upward, even though he thought he was doing the contractions well and he might have thought that there was a problem with the system and not a problem with the amplitude of the his contraction. Moreover, even if the contractions that he realizes vary, for example as a function of the humidity level, the external electric or magnetic field or his own psychological or physical conditions, he will be able to take this into account in order to realize the pivot of the elbow. that he wishes.

  According to a particularly preferred embodiment, the information signal is an auditory signal, and in particular in the form of musical notes as a function of the information to be transmitted.

  According to an even more preferred embodiment, and in particular allowing great discretion with respect to other persons, the prosthesis comprises an atrium connected to the auditory information device.

  According to a preferred embodiment of the invention, the set values consist of one or more minimum contraction values and one or more maximum contraction values, the signal then having three forms depending on whether the detected value is less than the minimum value, greater than the maximum value or within the minimum value / maximum value range.

  An embodiment of a "myoelectric" prosthesis according to the invention will now be described by way of illustration only, with reference to the drawings in which: FIG. 1 is a block diagram of a prosthesis according to the invention; FIG. 2 represents a block diagram of the control card of FIG. 1; Figure 3 shows a circuit diagram of the microcontroller of the prosthesis of Figures 1 and 2; Figure 4 is an overview of an elbow prosthesis; and Figure 5 shows in a voltage-time coordinate system possible stimuli due to a contraction of a muscle and how it can be determined that they are to be considered as strong stimuli or weak stimuli.

  In Figure 4, there is shown in perspective view an example of elbow prosthesis. A socket 1 allows the junction of this prosthesis to the wearer of the prosthesis. The prosthesis also comprises a body 2 of prosthesis inside which are on the one hand motors 7 to move the hand, wrist and elbow according to different rotational or translational movements possible, a switch 3, a battery 4 5, sensors 6 (not shown in the figure) are connected on the one hand to the control card and on the other hand to the healthy muscles of the person wearing the prosthesis, by being connected to these healthy muscles so as to be able to capture the amplitude of the contraction of the muscle in question, especially through the potential difference caused by the movement of anions and cations in the muscle cells.

  FIG. 1 represents a block diagram showing the operation of the prosthesis according to the invention. The miotic sensors or electrodes send signals after passing through a block 10 for shaping the sensor signals to the microcontroller. The control card can be switched on or off via the switch 3 and receives a power supply via the battery 4, here a 7V battery. In addition, the microcontroller or the card control 5 can be connected for example to a PC-type computer via a serial link for its programming, in particular the programming of information such as threshold values. In addition, the microcontroller 5 outputs sounds after amplification and passage through the block 11 of amplification and sound creation to an atrium 12 connected to the person wearing the prosthesis. Finally, the microcontroller is connected to the motors that operate the different parts of the prosthesis through the block 13 for measuring the current of the motors.

  The microcontroller is shown in FIG. 2. The microcontroller described here is a ST52X430 microcontroller from STMicroelectronics. It comprises a fuzzy logic module which makes it possible to produce the module for adapting the thresholds. It is an 8-bit controller of the FIVE family manufactured by STMicroelectronics that has a Boolean core and a fuzzy logic core. It also has an analog digital converter, synchronizers, a serial communication module and a sleep mode that minimizes the energy consumed. The microcontroller comprises 28 legs, PC1 / MOS1, PCOIC4 and B7, PB6, PB5, PB4, PB3, PB2, PB1, PC2, PC3, PC4, PC5, PA7, PA6, PAS, PA4, PA3, PA2, PA1, PAO, RESET VSS, VPP, OS IN, OS OUT and VDD. The process steps performed by the microcontroller are introduced via the ISP. The data related to the data processing, for example the threshold values, are provided via the serial link.

  For example, in the case shown in the figure, signals from the sensors 6 are taken with two tabs labeled sensor 2 and sensor 1. These data are inputted to the microcontroller 5 which, depending on the values received, and after signal processing. sensors for comparison with threshold values, comparison with threshold values provides control values for eg the wrist control motor, the hand control motor and the elbow control motor. Two motors for the wrist, two motors for the hand and two motors for the elbow are provided so that they can be turned in one direction or the other.

  A first possibility concerning the processing of the signals coming from the myoelectric electrodes is to introduce, via the serial link, two minimum threshold values, one for each sensor and two maximum threshold values, one for each sensor. Each sensor signal is then compared to the respective minimum threshold value and maximum threshold value. If the sensor signal is below the minimum threshold value, the music note is sent to the wearer of the prosthesis via the headset. If, on the other hand, the sensor signal is greater than the threshold values, the ground music note is sent. In the case where the signal of the sensors is in the range between the minimum value and the maximum value of threshold, it is sent a note of music, for example mi, or even it is nothing sent and in addition, the wrist, the hand and the elbow are controlled in accordance with the sequence of the received sensor signals.

  A stimulus usually has the shape of an increasing curve, then decreasing for a short time. For example, we can see in Figure 5 the stimuli whose shape has been approximated by triangles. According to the system described above, to determine whether a signal is strong or weak, one measures its maximum value, that is to say the tip of the triangle. If it exceeds the high threshold, it is a weak signal. If it does not exceed the low threshold, it is a weak signal. The disadvantage of this type of measurement is that one has to wait long enough for the stimulus to be fully measured to obtain control of the wrist, elbow, and musical notes. The latency or inertia of the system can be unpleasant for the wearer of the prosthesis.

  Another way of determining strong signals, weak signals and suitable signals is to provide in advance a steep slope and a low slope in addition to a high threshold and a low threshold.

  In the case where the signal departure slope (that is, the part before the stimulus peak) lies to the left of the strong limit slope, it is determined that it is a signal strong whatever ultimately the value finally taken by the top. If it is to the right of the low limit slope, it is a weak signal whatever ultimately the value finally taken by the vertex. It is thus assumed that statistically, in the case of a steep slope (to the left of the strong limit slope) the peak will be in most cases beyond the maximum threshold value, and conversely in the case of a weak slope. . In between, this is an acceptable signal. Then, we can further refine this determination by using the high threshold and the low threshold and by deciding that if the low threshold is not exceeded in the case of a slope between the strong limit slope and the low limit slope, it is a weak signal and if the high threshold is exceeded, it is a signal too strong. Once the "strength" of the signal is determined, it is then ordered to send the musical notes according to this force.

  Several types of information can be provided by the system according to the invention. For example, a first type of information can help the patient understand the operation of the prosthesis and what movement or action he has selected. Assuming that the patient has to do a combination of contractions to select a particular movement (for example the rise of the left forearm and then its rotation to the right), he can be informed that the control card has understood his message by the sending of an audible signal indicating, for example, what movement he wishes to perform. To do this, musical notes can be assigned to each given movement. Otherwise, the command card can simply be sent with recorded speech signals such as "upward rotation of the left forearm and then leftward rotation".

  A second type of information allows the patient to interact with the control card. It can for example perform a series of contractions to select a function. This dialogue can also allow the patient to perform an adjustment of its electrodes according to its capabilities.

  A third type of information is most important for prosthetic wearers who have difficulty adjusting contractions and who do not understand why their prosthesis is not working well. In this case, the patient makes a contraction, the system returns to him an information giving him an indication on the intensity of the signal (too strong, too weak or good) on each sensor. If the contraction is too strong or too weak, he has the information and he can try to modify this contraction to make an amplitude contraction acceptable for the movement or the selection of movements that he wishes to realize.

Claims (6)

  1. prosthesis of a member of the body of the human being comprising a body (2) of prosthesis, intended to replace at least partly the member, at least one motor (7) mounted to impart at least one movement to the body (2) of prosthesis, at least one sensor (6) of voltage, intended to be arranged to capture at least one tension created by the contraction of a muscle of the body of the human being; and a control unit (5) which controls the motor (s) to move the body (2) of the prosthesis according to the value of said at least one sensed voltage or a value related thereto, characterized in that an information device is provided for sending at least one information signal to the human carrying the prosthesis, said at least one information signal being a function of the deviation or deviations between the detected value of the at least one voltage or the value related thereto and one or more setpoints.   2. Prosthesis according to claim 1, characterized in that the information signal is an auditory signal, and in particular in the form of musical notes according to the information to be transmitted.   3. Prosthesis according to claim 1 or 2, characterized in that the prosthesis comprises an atrium connected to the auditory information device.   4. Prosthesis according to one of claims 1 to 3, characterized in that the set values consist of one or more minimum contraction values and one or more maximum contraction values, the signal then taking three forms. according to whether the detected value is less than the minimum value, greater than the maximum value or included within the minimum value / maximum value range.   5. Prosthesis according to one of the preceding claims, characterized in that the threshold values consist of a high limit slope value and a low limit slope value, the initial slope of the contraction or of the voltage curve. detected being compared with these two values of high and low limit slopes, and the information signal taking a first form if this initial slope is greater than the strong limit slope, a second form if this initial slope is less than the low limit slope. and a third form in the case of an initial slope between the two low and high limit slope values.   6. Prosthesis according to claim 5, characterized in that for determining said third form, the value of the vertex is compared with two high and low threshold values and the first form of signal is also sent if the strong threshold value is exceeded and the second form of signal being sent if the low threshold value is not exceeded and a third form of signal, in particular a zero signal (no signal) being sent if the value of the peak is between the two threshold values strong and weak.