SE441976B - SET TO DRIVE AND WELD ITEMS FOR ELECTRICALLY DRIVEN PROCESSES, MANIPULATORS AND SIMILAR AND DRIVER UNIT - Google Patents

Abstract

A drive unit for electrically driven prostheses, manipulators and the like, for example, the gripping members of an artificial arm or industrial robot, comprises an electrical drive motor (2) having an output shaft which drives an active component, for example a gripping means, via a transmission arrangement (4). The output shaft (7a) of a brake-motor (7) has arranged thereon a sleeve provided with a part having a right-hand screw thread and a part having a left-hand screw thread in engagement with brake means such as shoes (8, 9) which upon activation of the brake-motor engage a brake disk (6a) connected to the output shaft (2a) of the drive motor. The brake-motor is activated upon completion of the movement of the drive motor and therewith locks the active component in the position to which it has been moved without the occurrence of play.

Description

Technique) describes a safety device for an artificial hand with which a special locking device is used to keep the fingers of the prosthesis in their closing position.

Prior art prostheses of this and similar types, in which one controls a drive motor which causes the movement of the active element, has the serious disadvantage that one cannot obtain a distinct positioning of the active element. This is related to the inertia that is always present in the system, and which means that the element cannot be made to stay in the exact position. Another disadvantage associated with this is that one cannot achieve clearance with such devices. As a rule, it is also not possible to obtain breakability, which is a very important requirement for most types of prostheses. Namely, if the prosthesis is locked in a certain position and cannot be broken, this can in many cases lead to serious damaging effects.

Another serious inconvenience associated with most hitherto known prostheses is that they must be manufactured with very precise tolerances for satisfactory function.

Object of the invention An object of the invention is accordingly to provide a method of the above kind, which obviates stated disadvantages of known drive systems and which allows accurate positioning of the active elements of the prosthesis without, for example, the gripping force being lost due to play in the prosthesis or corresponding.

Another object is to provide a drive system of the type indicated which, even in the locked position, allows easy breakability of the active element.

Another important object is to provide a drive system for prostheses, manipulators and the like which allows simple and reliable control by electronic means and which can thereby be more easily adapted to the varying requirements set in different contexts, e.g. of different patient categories and the environment in which a robot is to work.

A further object is to provide a drive and control system of the type indicated which operates reliably without precise manufacturing tolerances for the components included.

Brief description of the invention These and other objects are fulfilled by a method according to the invention which in its broadest aspect is characterized in that in addition to the drive motor a brake motor is also used which is activated during the final stage or after the movement to lock the element in the occupied position.

By using according to the invention a special brake motor which ensures accurate locking of the active element in an occupied position, distinct, play-free positioning of the active element is made possible. At the same time, easy degradability of the active element is allowed, when required.

The separate electric motors for the drive and locking movements mean that the arrangement as a whole can be given a simple and robust design, which in turn leads to reliable function without precise manufacturing tolerances.

As a rule, a series motor is used for the drive movement, which thus means that the supplied current increases when a resistance occurs to the movement of the active element, for example when it grips an object. In a preferred embodiment of the invention, this can be used for controlling the brake motor by activating the brake motor when the control of the current supplied to the drive motor exceeds a predetermined value.

Alternatively, it is possible to give, for example, an impulse for starting the brake motor, when the movement of the active element ceases or begins to stop, for example in connection with engagement with an object.

In a special application of the invention for controlling prostheses, in which myo-signals are utilized in a known manner for controlling the movements of the drive motor, such myo-signals are also used for controlling the brake motor. Special advantages are then offered when the brake motor is to be activated for release, ie. caused to rotate in the opposite direction in relation to the direction of rotation when locked.

The invention also relates to a drive unit for electrically operated prostheses, manipulators and the like, e.g. the gripping device of arm prostheses and robots, which drive unit comprises an electric drive motor with an output shaft, a gear device for transmitting the movement of the output shaft to a drive shaft for an active element, e.g. a gripping means, and which drive unit is characterized by an electric brake motor, the output shaft of which cooperates with brake shoes arranged to read the active element in an engaged position by engaging an element operatively connected to the output shaft of the drive motor, and control means arranged to activate the brake the motor at the end of or after completion of the movement of the active element. in a preferred embodiment in practice, the output shaft of the brake motor carries a sleeve with a right-handed portion in self-braking engagement with one brake shoe and a left-handed portion in self-braking engagement with the other brake shoe.

This results in a mechanically simple and reliable arrangement that can quickly exert large braking forces.

The self-braking of the threaded parts means that the braking force is maintained despite the fact that the drive current to the brake motor is interrupted as soon as the brake shoes are switched on, whereby the current output of the drive and brake unit can be minimized.

However, in the stated device a problem arises to the extent that the rotating torque of the brake motor is usually not sufficient to directly allow the release of the jaws when reversing the direction of rotation. In a preferred embodiment of the invention, however, this problem is solved in that the shaft of the brake motor carries an eccentric abutment element which in said reversal of the direction of rotation after approx. 1/2 lap clearance exerts an impact against a part of the shaft sleeve. The said impact action is sufficient to bring the self-braking to an end, after which the movement of the brake shoes to the full release position takes place without difficulty.

A preferred embodiment is characterized in that the output shaft of the drive motor carries a with it concentric brake drum with a brake disc, against which the brake shoes engage. A disc brake of this kind becomes extremely effective despite its simple manufacturing design.

The shaft of the brake drum can further partially enclose the drive motor, which thus in practice means that the two motors, namely the drive motor and the brake motor, occupy a position close to each other and thus the available space - which is often small in a prosthesis of this type - - be taken care of in the best possible way. In other words, the invention allows an extremely compact drive and brake unit to be achieved.

For efficient control of both drive and brake motor, the control means may comprise a sequence part with two or more derivation units for opening and closing the brake at the desired time and one or more delay circuits to prevent movement of the drive motor before the brake is released and prevent play before the brake has gripit.

Derivative units and delay circuits of the type indicated constitute simple and inexpensive electronic components which find advantageous use in a drive and brake unit according to the invention.

In addition to prostheses, a drive and brake unit according to the invention can find advantageous use also in many other contexts, for example in various types of manipulators such as robots and the like. The control signals for the activation of the two motors are then generally different in that the myo-signals are not used for the control of the motors.

The invention will be described in more detail below with reference to an embodiment thereof shown in the accompanying drawings.

Brief description of the drawings Fig. 1 is a cross-section through a drive unit according to the invention for use, for example, in an arm or hand prosthesis.

Fig. 2 is a section along the line II-II in Fig. 1.

Fig. 3 is an end view of a part of the drive unit according to Fig. Z. "In Fig. 4, a hand prosthesis with a rigid three-point grip provided with a built-in drive unit according to the invention schematically illustrates.

Fig. 5 is a side view of the hand prosthesis of Fig. 4.

Fig. 6 is a block diagram illustrating examples of electronic components of a drive unit according to the invention.

Fig. 7 is a diagram showing examples of control signals which are used for the control of the drive unit.

Description of the preferred embodiment With reference first to Figs. 1-3, the number 1 illustrates a drive unit which can be used, for example, in an electrically driven hand prosthesis or an industrial robot.

The drive unit comprises an electric motor 2 with an output shaft 2a. The drive motor can be of a more or less conventional type and is powered by a 6 V battery.

The output shaft 2a carries a timing belt gear 2b with an applied timing belt 3 which is passed over a timing belt wheel 4b on an input shaft 4a to a planetary gearbox 4. Its output shaft 4c carries a timing belt drive 4d with an applied timing belt 5.

The output shaft 2a of the electric motor also carries a concentrically arranged drum 6, which partially encloses the drive motor 2. The drum 6 centrally supports a radially directed and circumferentially circumferential brake disc 6a.

Under the drive motor 2 there is a brake motor 7, the output shaft 7a of which carries a shaft sleeve 7b which has a left-hand thread and a right-hand threaded portion. Each of these parties is in self-inhibiting engagement with a brake shoe 8 resp. 9, which upon rotation of the brake motor in one direction engages the disc 6a on the drum 6.

As can be seen from Fig. 3, the shaft 7a 8402225-51 7 of the brake motor also carries an eccentric stop element 7c which, when reversing the direction of rotation of the jaws 8, '.

Figures 4 and 5 illustrate an electric hand prosthesis 10 with a rigid three-point grip. The gear belt 5 applied to the output shaft 4c of the gearbox 4 is passed over a gear or sprocket 11 which is connected to the movable finger 13 of the prosthesis. This can cause engagement against a thumb 14 connected thereto via a link 15.

After completion of the movement of the finger 13 towards the thumb 14 - which takes place after activation of the drive motor 2 - the brake motor 7 is activated, the brake shoes 8, 9 moving rapidly towards each other during engagement with the brake disc 6a on the drum 6, whereby accurate, clear locking of the finger 13 and thumb 14 in the occupied position is achieved.

Both the brake motor 7 and the drive motor 2 are deactivated immediately thereafter, the locking engagement being maintained with the aid of the present self-braking in the threaded engagement between the brake shoes 8 resp. 9 and the corresponding threaded part of the shaft sleeve 7b.

When the finger grip is to cease, the brake motor is activated for movement in the opposite direction - which can be done using myo-impulses - whereby the eccentric stop element 7a shown in Fig. 3 exerts the above-mentioned percussion force against the shaft sleeve part 7b '.

When the brake shoes 8, 9 are released from the brake disc 6a, the drive motor 2 is activated in the opposite direction for reversed movement of the finger 13 and the thumb 14.

From the block diagram shown in Fig. 6 it appears that the control means comprise a sequence part with four derivation units for detecting started resp. In the diagram shown in Fig. 7, these four signals are illustrated below B. Their function is to open resp. close the brake at the right moment. As a rule, the brake must be opened before the drive motor 2 receives an impulse 8 8222223-5 8 for movement when the moving element is activated and that the brake must strike when a negative derivative of the myo signal is detected. The current to the brake motor constitutes an amplification of the time derivative of the myo-signal.

The block diagram in Fig. 6 further shows that the drive motor 2 has delay circuits in order to prevent movement before the brake is deactivated, and to prevent play before the brake is activated.

When the patient is to grip an object with the help of the prosthesis, this is done by stretching the muscle on either the lower or upper side of the arm (contracture).

The contraction gives rise to a myo signal and the drive motor is activated. When the patient feels that the prosthesis grips (ie the force is built up) about the object, he relaxes in the muscle, after which a short pulse is given to the brake motor. The current supplied to the brake motor thus constitutes an amplification of the time derivative of the myo signal. The brake shoes engage against the brake disc, so that the prosthetic grip is kept clear. Only when the short current pulse to the brake motor has ceased, the current Lill drive motor is cut off. _ The control electronics include one final stage for the drive motor and one for the brake motor. The final stage of the drive motor is suitably complemented by a so-called. battery saving circuit, which prevents unnecessary power consumption during muscle contraction.

The battery saving circuit thus ensures that the drive motor is never activated for more than a predetermined time, e.g. 1.5 sec.

The various active components of the circuits, including associated capacitors, are in practice suitably miniaturized, albeit discrete. This type of circuit is usually called a hybrid circuit.

For the sake of completeness, it can be mentioned that the current to the drive motor constitutes an amplification of the myo signal with a certain time delay Tf i A myo signal always corresponds to a muscle contraction, which depending on whether the muscle contraction takes place on the upper or lower side of the arm produces a positive or negative myo signal, which in turn supplies power to the drive motor in one or the other direction.

Industrial applicability A drive unit equipped with a brake motor of the type described can be applied in many other contexts, for example in various types of manipulators such as industrial robots and the like. The principle for the activation and deactivation of the two motors then becomes essentially the same, even though the control signals themselves can be generated in varying ways depending on the environment or the circumstances.

Claims (9)

Claims 8402225-5 1. Methods of driving and locking elements to electrically driven prostheses, manipulators and the like, e.g. gripper means of arm prostheses and robots, a drive motor being used, the movement of which is supplied via a gear to the element for performing its movement, characterized in that a brake motor is also used which is activated during the final stage of or after the movement to lock the element in the occupied position. 2. A method according to claim 1, characterized in that the brake motor is activated when the strength of the current supplied to the drive motor exceeds a predetermined value. 3. A method according to claim 1 or 2 for driving prostheses, wherein mio-signals are used for controlling the movements of the drive motor, characterized in that myo-signals are used for controlling the brake motor as well. Drive unit for electrically driven prostheses, manipulators and the like, e.g. the gripping means of arm prostheses and robots, which drive unit comprises - an electric drive motor (2) with an output shaft (2a), a gear device (4) for transmitting the movement of the output shaft (2a) to a drive shaft for an active element, for example a gripping member (13), characterized by an electrically driven brake motor (7), the output shaft (7a) of which cooperates with brake shoes (8, 9) arranged to be operatively connected to an output shaft (Za) of the drive motor elements (Ga) lock the active element (T3) in an occupied position, and control means arranged to activate the brake motor at the end of or after completion of the movement of the active element. Drive unit according to claim 4, characterized in that the output shaft (7a) of the brake motor carries a sleeve (7b) with a right-handed portion in self-braking engagement with one brake shoe (eg 8) and a left-hand section in self-inhibiting engagement with the other brake shoe (eg 9). Drive unit according to Claim 5, characterized in that the output shaft (7a) of the brake motor (7) carries an eccentric stop element (7c) which, when reversing the direction of rotation of the jaws (8, 9) after approx. 1/2 lap clearance exerts impact on a part (7b ') belonging to the shaft sleeve (7b). Drive unit according to one of Claims 4 to 6, characterized in that the output shaft (2a) of the drive motor (2) carries a with it concentric brake drum (6) with a brake disc (6a), against which the jaws (8 , 9) intervenes. Drive unit according to Claim 77, characterized in that the brake drum (6) partially encloses the drive motor (2). Drive unit according to one of Claims 4 to 8, characterized in that the control means comprise a sequence part with two or more derivation units for opening and switching on the brake at the desired instantaneous moment and one or more delay circuits for preventing movement of the drive motor. before the brake is released_and prevent play before the brake has applied.