IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0867933
(2009-02-20)
|
등록번호 |
US-8706305
(2014-04-22)
|
국제출원번호 |
PCT/CA2009/000199
(2009-02-20)
|
§371/§102 date |
20100817
(20100817)
|
국제공개번호 |
WO2009/103159
(2009-08-27)
|
발명자
/ 주소 |
- Jiang, Xin Xiang
- Nikanpour, Darius
|
출원인 / 주소 |
|
대리인 / 주소 |
|
인용정보 |
피인용 횟수 :
0 인용 특허 :
9 |
초록
▼
Control feedback for regulating strain output of a shape memory alloy (SMA) actuator using a stress sensor for outputting an indication of a mechanical resistance applied against the SMA actuator, and a state sensor for outputting an indication of a state of actuation of the SMA actuator has been fo
Control feedback for regulating strain output of a shape memory alloy (SMA) actuator using a stress sensor for outputting an indication of a mechanical resistance applied against the SMA actuator, and a state sensor for outputting an indication of a state of actuation of the SMA actuator has been found to be surprisingly accurate. Advantageously feedback detection can be provided with sensors that have low power requirements and can be controlled with simple electronics.
대표청구항
▼
1. A control feedback mechanism for regulating strain output of a shape memory alloy (SMA) actuator comprising: a stress sensor for outputting an indication of a force to a control processor, the stress sensor being a strain gauge for computing a load on an SMA element of the SMA actuator;a state se
1. A control feedback mechanism for regulating strain output of a shape memory alloy (SMA) actuator comprising: a stress sensor for outputting an indication of a force to a control processor, the stress sensor being a strain gauge for computing a load on an SMA element of the SMA actuator;a state sensor for outputting an indication of an amount of Austenitic phase of the SMA element relative to Martensitic phase, the state sensor comprising circuit elements for outputting a signal corresponding to an electrical resistance across the SMA element to the control processor;the control processor for computing an actuation signal for selectively heating the SMA element in dependence on physical characteristics of the SMA element, a desired strain output value of the SMA actuator, and the indications of force and amount of Austenitic phase; anda circuit for delivering the actuation signal as an electrical signal to selectively deliver power from a power source for direct electrical resistive heating of the SMA element; wherein the state sensor outputs the indication of amount of Austenitic phase to the control processor, regardless of whether the SMA actuator is actuated, by supplying a current to the SMA element that is less than a current required for SMA actuation, when the SMA element is not being heated. 2. The control feedback mechanism of claim 1 wherein selectively heating the SMA element is performed exclusively by direct application of current through the SMA element via the circuit. 3. The control feedback mechanism of claim 2 wherein the SMA actuator is of a contraction-type, and the SMA element is in the form of a wire, ribbon, rod, strip or tube, or an assembly of one or more of the above, the SMA element being made of a Ni—Ti or Ni—Ti—Cu alloy. 4. The control feedback mechanism of claim 3 wherein the circuit comprises a first resistor connected in series with the SMA element, and a switch for selectively closing the circuit in response to a signal from the control processor to apply a controlled current through the SMA element. 5. The control feedback mechanism of claim 3 wherein the circuit comprises a first resistor connected in series with the SMA element, and a switch for selectively closing the circuit in response to the actuation signal from the control processor so that a predefined threshold power is applied to the SMA element. 6. The control feedback mechanism of claim 5 wherein the switch is a first transistor, and the circuit further comprises a bypass resistor connected in parallel to the first transistor and in series with the first resistor forming a first circuit branching between the first resistor and the first transistor, the bypass resistor being of a resistance selected to bypass the first transistor when the transistor is off while providing sufficient electrical power to allow an electrical resistance measurement of the SMA element, while applying a minimum current that is far less than the current required for actuation of the SMA element. 7. The control feedback mechanism of claim 6 wherein the control processor is adapted to compute the resistance across the SMA element (Rsma) using the formula: Rsma=Rf(V13−V12)/(V12−V11), where Rf is the first resistor, V11 is a voltage tap between the first resistor and the first circuit branching to the bypass resistor, V12 is a voltage tap between the SMA element and the first resistor, and V13 is a voltage tap between a power supply and the SMA element. 8. The control feedback mechanism of claim 6 further comprising a second circuit branching between the first resistor and the first transistor including in series a second bypass resistor and a second transistor, the second bypass resistor being of a resistance selected to apply a second electrical power to the SMA element, the second electrical power sufficient to maintain the SMA actuator in an actuated state, in response to the actuation signal from the control processor. 9. The control feedback mechanism of claim 3 wherein the control processor is adapted to determine the actuation signal in dependence on: the physical characteristics of the SMA element, the desired strain output value, and the indications of force and amount of Austenitic phase, and one or more of:a hysteresis function that depends on previously sent actuation signals;a modeled thermodynamic state of the SMA element environment;a measurement of a thermodynamic state of the SMA element environment; andan operating mode of the SMA actuator. 10. The control feedback mechanism of claim 1 wherein the state sensor comprises circuit elements including some of the circuit, for outputting an electrical resistance across the SMA element to the control processor. 11. The control feedback mechanism of claim 1, wherein the power source is a direct current (DC) power source. 12. The control feedback mechanism of claim 1 wherein reading from the strain gauge is also used to protect the SMA element from overloading of mechanical stress. 13. The control feedback mechanism of claim 1 wherein the strain gauge is located proximate a support for retaining one end of the SMA element. 14. The control feedback mechanism of claim 1 wherein the strain gauge is supplied power from the power source. 15. The control feedback mechanism of claim 1 wherein the strain gauge operates on the principle of electrical resistance varying with cross-section and length of a conductor. 16. The control feedback mechanism of claim 15 wherein: the strain gauge is thermally isolated from the SMA element;the strain gauge comprises a thermocouple for determining a temperature of the strain gauge, so that the force indication includes one of: a value resulting from readings of the strain gauge and the thermocouple; or both the readings of the strain gauge and the thermocouple;the strain gauge comprises two or more strain gauges arranged so that variation in response to a given change in temperature can be isolated and removed; orthe strain gauge comprises two or more strain gauges arranged for elongation and compression respectively in response to stress applied on the SMA element. 17. A method of controlling a shape memory alloy (SMA) actuator, the method comprising: receiving signals of internal electrical resistance of an SMA element and loading stress on the SMA element, as feedback for strain output regulation of the SMA actuator, the internal electrical resistance indicating an amount of Austenitic phase of the SMA element relative to Martensitic phase, and the loading stress output by a strain gauge located proximate a support for retaining one end of the SMA element;translating the signals of internal electrical resistance and loading stress into a strain output reading based on a pre-established correlation at a control processor; andusing the strain output reading as a feedback signal to regulate the strain output of the SMA actuator by delivering an actuation signal as an electrical signal to selectively deliver power for direct electrical resistive heating of the SMA element in dependence upon the strain output reading, wherein receiving the signal of electrical resistance is provided, regardless of whether the SMA actuator is actuated, by continuously supplying a current to the SMA element that is less than a current required for SMA actuation, when the direct electrical resistive heating is not applied. 18. The method of claim 17 wherein translating the signals and using the strain output reading involves computing the actuation signal in dependence on: the physical characteristics of the SMA element, the desired strain output value, and the indications of force and amount of Austenitic phase, and one or more of:a hysteresis function that depends on previously sent actuation signals;a modeled thermodynamic state of the SMA element environment;a measurement of a thermodynamic state of the SMA element environment; andan operating mode of the SMA actuator. 19. The method of claim 17 wherein the SMA actuator is of a contraction-type, and comprises a SMA element in the form of a wire, ribbon, rod, strip or tube, or an assembly of one or more of the above, the SMA element being made of a Ni—Ti or Ni—Ti—Cu alloy. 20. The method of claim 17 wherein regulating the strain output of the SMA actuator is performed exclusively by the direct electrical resistive heating of the SMA element.
※ AI-Helper는 부적절한 답변을 할 수 있습니다.