DE102014111460B4 - Actuator device with a shape memory material and robot and medical prosthesis with such an actuator device - Google Patents

Abstract

An actuator device comprising a plurality of fibers (101) or a plurality of shape memory material bundles (101) fixedly connected to each other at their respective fiber start / fiber bundle end and fiber end / fiber bundle end, along each fiber (101) / each Fiber bundle (101) a plurality of spaced apart, with the respective fiber (101) / the respective fiber bundle (101) thermally conductively connected Peltier-Eiemente (102) are arranged concentrically the respective fiber (101) or the respective fiber bundle (101) and a control means (103) for individually and independently controlling each of the Peltier elements (102).

Description

The invention relates to an actuator device with a temperature-controlled shape memory material. The proposed actuator device is preferably used in robotics, and there in particular as an artificial muscle for driving Roboterermanipulatoren or end effectors. The invention further relates to a robot with at least one such actuator device. The invention further relates to prostheses with at least one such actuator device.

Actuators for robots, in particular actuators for robotic manipulators or end effectors, should be sufficiently responsive, enable a discreetly adjustable gripping force, and be light and small.

Actuators with a temperature-controlled shape memory material are known. They are based on the ability of shape memory materials / alloys (FGL) to possess the capability of reversible phase transformation. The phase in which the shape memory alloy is located depends on the temperature. Martensite is present at low temperatures and austenite at high temperatures. The transition between the two phases is a hysteresis-related function of the temperature.

In the low temperature phase, the shape memory alloy is relatively easily deformable. It is possible to reverse mechanical deformation of shape memory alloys in the low temperature phase by supplying heat. The material remembers its original shape, with elongations of typically up to 8% possible. However, cooling a one-way material does not cause the FGL to return to the deformed state. Therefore, a preload force acting on the FGL is required to achieve deformation during cooling.

If the material is working against a load during re-deformation, very high forces can be generated with only small amounts of material used. The design of FGL actuators is flexible, typically wires and coil springs are common.

Actuators made of so-called shape memory material therefore use the peculiarity of this material to change the external shape depending on the material temperature. The thermal memory effect is an intrinsic property of shape memory alloys. Upon mechanical deformation below the martensite start temperature, the FGL returns to its original shape by heating and phase transition to the austenite phase occurs. After cooling and phase transformation into the martensite phase, this form is retained until re-deformed.

Thermally activated actuators having a shape memory material (eg, FGL wires) in the martensite state are activated by heating the material above an activation temperature. With respect to FGL wires, this generally causes the material to undergo phase transformation to austenite and contract in a manner that can be used to do work. Once the actuator is activated, the actuator typically has to undergo a relatively long cooling period in which its temperature is lowered below the transition temperature before it can be reactivated. During this cool down period, the actuator is not available to do work, so the duration of the cool down period adds significantly to the total operating bandwidth of the actuator.

Conventional methods of cooling, which merely involve exposure of the material to ambient conditions, are often inadequate and / or involve complex peripheral systems such as e.g. These problems arise in particular in generic actuators, which are exposed to a rapid successive activation and / or must cause an operation with a quick reset (eg <1 s).

To solve this problem is out of the DE 10 2011 102 597 A1 a thermally activatable actuator is known which uses a heat sink to accelerate the cooling in a thermal activation cycle. To experience faster cooling, the heat sink has a rate of thermal conductivity that is higher than the ambient rate. Furthermore, the heat sink automatically engages the actuator when the actuator is activated.

From the publication US Pat. No. 7,188,473 B1 For example, an actuator with shape memory material is known, which is controlled by means of a binary control. For this purpose, segments of shape-memory material, for example, are arranged serially or in a planar manner, the individual segments being individually controlled in each case.

From the publication JP 2001112796 A For example, an artificial heart muscle is known which comprises a strand of shape-memory material, a plurality of Peltier elements being arranged along the strand. The Peltier elements are controlled individually and can thus lead to a targeted change in shape of the strand.

From the publication US 2009/0216083 A1 an endoscope-like device is known, which preferably has shape memory material elements for the external change in shape, which are formed by individualized Applying an electrical voltage, an electric current or heat cause a linear movement of the shape memory material elements, so that the outer shape of the device can be selectively changed.

Furthermore, from the document US 2013/0116712 A1 a device and a method for endoscopy known.

The object of the invention is to improve a generic actuator in terms of its reaction rate and thus an actuator eg. To provide the drive for end effectors, which has improved positioning and a more precisely adjustable gripping force.

The invention results from the features of the independent claims. Advantageous developments and refinements are the subject of the dependent claims. Other features, applications and advantages of the invention will become apparent from the following description, as well as the explanation of embodiments of the invention, which are illustrated in the figures.

The object is achieved with an actuator device which comprises: a plurality of fibers or a plurality of shape-memory material bundles which are fixedly connected to each other at their respective fiber start / fiber bundle beginning and at their respective fiber end / fiber bundle end, with several along each fiber / fiber bundle spaced apart, with the respective fiber / the respective fiber bundle thermally conductively connected Peltier elements are arranged, which respectively surround the respective fiber or the respective fiber bundle concentrically, and which serve for active local cooling, and a control means with which each of the Peltier Elements individually and independently of each other is controllable.

In the present case, the term "actuator" is understood to mean the fiber or the fiber bundle made of a shape memory material with the Peltier elements arranged thereon or the heating elements mentioned later. The term "actuator device" is understood herein to mean the actuator together with the control means.

In the present context, the term "Peltier element" is understood to mean an electrothermal converter which, based on the Peltier effect (according to Jean Peltier, 1785-1845), generates a temperature difference at current flow or a current flow (Seebeck effect) at temperature difference.

By means of the plurality of Peltier elements arranged along the fibers or the fiber bundles, a local or section-wise, active local cooling of the individual fibers or of the respective fiber bundles is possible. In contrast to the prior art, a sufficiently fast and in particular locally targeted cooling of the actuator is achieved with the proposed actuator device. The local cooling makes possible a continuous position or force regulation by means of the fibers or the fiber bundles, which can be used in particular for end effectors of robots or medical prostheses. The fibers or fiber bundles advantageously have a round cross-section.

A development is characterized in that p-type and n-type semiconductor elements of the Peltier elements are each formed in a ring shape and enclose the fibers or fiber bundles. The annular Peltier elements can be easily manufactured and continue to allow easy production of the actuator.

Advantageously, the Peltier elements are connected by a thermally conductive elastic polymer material with the fiber or the fiber bundle. Further advantageously, electrical connections to the p-type and the n-type semiconductor elements of the respective Peltier elements advantageously consist of an electrically conductive elastic polymer material. Both allow a wider range of motion of the actuator or reduces its movement restrictions by the annular Peltier elements or its electrical contacts.

A particularly preferred development of the proposed actuator device is characterized in that heating elements for local heating of the fibers or the fiber bundles are additionally arranged along the fibers or the fiber bundles, and the control means is also designed for individual control of the individual heating elements. Advantageously, the heating elements also surround the fibers or the fiber bundles completely concentrically. Further advantageously, the heating elements and the Peltier elements are arranged alternately along the fibers or the fiber bundles. These developments allow complete local or partial temperature control of the fibers or fiber bundles, i. a local heating or local cooling and thus a very precise control of the positioning or the deformation of the fibers or fiber bundles. As heating elements Peltier elements can also advantageously be used. In this respect, a preferred embodiment exclusively on Peltier elements, which surround the fibers or the fiber bundles in each case annular, and which are operated depending on the requirements each as a heating and cooling elements.

The actuator device according to the invention is thus characterized in that the actuator itself comprises a plurality of fibers or a plurality of fiber bundles of a shape memory material, wherein along the respective fibers or the respective fiber bundles spaced apart, with the respective fiber or the respective fiber bundle thermally conductively connected Peltier Elements are arranged, which surround the respective fiber or the respective fiber bundle concentrically (completely) fiber, and which serve for the active local cooling of the fibers or the fiber bundles, and wherein the fibers or the fiber bundles at their respective fiber beginning or fiber bundle beginning and at their respective fiber end or fiber bundle end are firmly connected to each other. The actuator is thus comparable to a muscle in which individual muscle strands are separately adjustable in length and shape, the muscle fibers being connected at their beginning and end, thus having two common points of application for transmitting a force effect.

The invention relates to a robot with an actuator device, as described above. Advantageously, the robot comprises a plurality of these devices for driving a robot arm or effector, wherein the control means is adapted to make the control of the Peltier eggs depending on a predetermined position or orientation or speed or force of the robot arm or the effector.

The invention further relates to a medical prosthesis, for example a hand, arm or leg prosthesis, with an actuator device, as described above. Advantageously, the prosthesis on several of these devices for driving example. Of limbs, wherein the control means is designed to make the control of the Peltier elements depending on a predetermined position or orientation or speed or force of the prosthesis.

Further advantages, features and details will become apparent from the following description in which - where appropriate, with reference to the drawings - at least one embodiment is described in detail. The same, similar and / or functionally identical parts are provided with the same reference numerals.

• 1 ein Ausführungsbeispiel der vorgeschlagenen Aktor-Vorrichtung.

Show it:

• 1 An embodiment of the proposed actuator device.

1 shows an embodiment of the proposed actuator device. The device comprises an actuator with a fiber 101 with a round cross section of a shape memory material. Along the fiber 101 are spaced apart and alternating Peltier elements 102 for local cooling and heating elements 104 arranged for local warming. The Peltier elements 102 and the heating elements 104 enclose the fiber 101 each completely concentric. Both the Peltier eggs 102 , as well as the heating elements 104 are with the fiber 101 thermally conductive connected. The actuator device further comprises a control means 103 with which each of the Peltier elements 102 and each heating element 104 individually and independently controllable.

Although the invention has been further illustrated and explained in detail by way of preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention. It is therefore clear that a multitude of possible variations exists. It is also to be understood that exemplified embodiments are really only examples that are not to be construed in any way as limiting the scope, applicability, or configuration of the invention. Rather, the foregoing description and description of the figures enable one skilled in the art to practice the exemplary embodiments, and those skilled in the art, having the benefit of the disclosed inventive concept, can make various changes, for example, to the function or arrangement of individual elements recited in an exemplary embodiment, without Protected area, which is defined by the claims and their legal equivalents, such as further explanation in the description.

LIST OF REFERENCE NUMBERS

101

Fiber or fiber bundle

102

Peltier element / e

103

control means

104

Heater / e

Claims (10)

Actuator device comprising - a plurality of fibers (101) or a plurality of shape memory material bundles (101) fixedly connected to each other at their respective fiber start / fiber bundle end and at their respective fiber end / fiber bundle end, along each fiber (101) / each Fiber bundle (101) a plurality of spaced apart, with the respective fiber (101) / the respective fiber bundle (101) thermally conductively connected Peltier-Eiemente (102) which respectively surround concentrically the respective fiber (101) or the respective fiber bundle (101) and which serve for active local cooling, and - a control means (103) with which each of the Peltier elements (102) individually and independently controllable. Actuator device after Claim 1 in which the fibers (101) or fibers of each fiber bundle (101) have a round cross-section. Actuator device after Claim 1 or 2 in which p-type and n-type semiconductor elements of the peltier elements (102) are each formed in a ring shape and the respective fiber (101) / concentrically surround the respective fiber bundle (101). Actuator device according to one of Claims 1 to 3 in that the Peltier elements (102) are connected to the fibers (101) or the fiber bundles (101) by a thermally conductive elastic polymer material. Actuator device according to one of Claims 3 to 4 in which electrical connections to the p-type and n-type semiconductor elements of the peltier elements (102) consist of an electrically conductive elastic polymer material. Actuator device according to one of Claims 1 to 5 in which heating elements (104) for local heating of the fibers (101) / of the fiber bundles (101) are arranged along the fibers (101) / of the fiber bundles (101), and the control means (103) for individually controlling the individual heating elements (104 ) is executed. Actuator device after Claim 6 in which the heating elements (104) and the Peltier elements (102) are alternately arranged along the fibers (101) / the fiber bundle (101). Robot with an actuator device according to one of Claims 1 to 7 Robot after Claim 8 wherein a plurality of the actuator devices are for driving a robotic arm or effector, and the control means (103) is adapted to control the Peltier elements (102) in accordance with a predetermined position setting or guidance or speed setting or force setting of the robotic arm or effector make. Medical prosthesis with an actuator device according to one of Claims 1 to 7 wherein the prosthesis is designed as a hand prosthesis or as an arm prosthesis or as a prosthetic leg.

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