IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0662709
(2010-04-29)
|
등록번호 |
US-8378610
(2013-02-19)
|
우선권정보 |
DK-2009 00569 (2009-05-01) |
발명자
/ 주소 |
- Jensen, Svend Erik Knudsen
|
출원인 / 주소 |
|
인용정보 |
피인용 횟수 :
1 인용 특허 :
3 |
초록
▼
A linear actuator includes a housing with a reversible DC-motor, which through a transmission can displace an activation element between two end positions, where an further switch located in the longitudinal direction of the spindle is activated and deactivated when a spindle nut passes during its t
A linear actuator includes a housing with a reversible DC-motor, which through a transmission can displace an activation element between two end positions, where an further switch located in the longitudinal direction of the spindle is activated and deactivated when a spindle nut passes during its travel on the spindle and provides information for a calculation model which continuously calculates the position of the spindle nut on the spindle so that the calculation model in the positions where the further switch is activated by the spindle nut is calibrated to show an absolute position which is entered as a reference point in the control.
대표청구항
▼
1. Linear actuator comprising a reversible DC-motor,a transmission,a spindle in driving connection with the DC-motor through the transmission,a spindle nut arranged on the spindle and secured against rotation, such that it is displaceable between two end stop positions on the spindle, at least one e
1. Linear actuator comprising a reversible DC-motor,a transmission,a spindle in driving connection with the DC-motor through the transmission,a spindle nut arranged on the spindle and secured against rotation, such that it is displaceable between two end stop positions on the spindle, at least one end stop switch for interrupting the current to the DC-motor in the two end positions of the spindle nut or signaling of the end stop position,a position determination system for determining the position of the spindle nut on the spindle,wherein the position determination system comprises at least one further switch that could be activated by the spindle nut and a microprocessor containing a calculation model, which calculation model includes i) one or more of the physical parameters of the actuator and which as input has ii) dynamic values for absorbed power, and where the spindle nut's activation of the at least one end stop switch and the at least one further switch iii) gives a signal for calibration of the position of the spindle nut on the spindle calculated from the calculation model. 2. The linear actuator according to claim 1, wherein the activation area, where the spindle nut activates the further switch covers a distance on the length of the spindle. 3. The linear actuator according to claim 1, wherein a new position of the spindle nut is indicated both by activation and deactivation of the further switch. 4. The linear actuator according to claim 3, wherein the position of the spindle nut in connection with the activation and deactivation of the further switch is determined based on the direction of movement of the spindle nut. 5. The linear actuator according to claim 1, wherein the position determination system has means for reading the state of the end stop switches and the further switches. 6. The linear actuator according to claim 1, wherein the position determination system has means for measuring the voltage and current of the DC-motor. 7. The linear actuator according to claim 1, wherein the means for calculating changes of the position of the spindle nut is a calculation model, which includes physical parameters of the actuator which at least comprises the motor constant and the resistance loss, at which the immediate motor speed may be calculated. 8. The linear actuator according to claim 7, wherein the immediate motor speed is calculated by inserting the measured values for the motor voltage and motor current in the calculation model. 9. The linear actuator according to claim 8, wherein the change of the position of the spindle nut is calculated by incorporation of the immediate motor speed over the time where the motor has been activated. 10. The linear actuator according to claim 1, wherein the position determination system is equipped with a memory which continuously is updated with information about the position of the spindle nut on the spindle in that the information is delivered as a contribution or deduction measured over a period of time, which is summed up in the memory and, where the position of the spindle nut when activating or deactivating a switch calibrates the contents in the memory to a predetermined value in the control, which corresponds to the exact position of the spindle nut on the spindle. 11. A method of determining the position of a spindle nut on a spindle of a linear actuator where the spindle is driven by a DC-motor, comprising the steps of: registering a known position of the spindle nut on the spindle,calculating the travel of the spindle nut on the spindle from the rotational speed of the spindle and the pitch of the spindle, andcalculating the position of the spindle by the travel of the spindle nut relative to the known position. 12. A method according to claim 11, comprising registering the motor terminal voltage and the motor current, determining the resistance Rloss in the motor and a motor constant, and calculating the rotational speed of the spindle from the formula: Spindle speed=(motor terminal voltage−motor current*Rloss)*motor constant. 13. The method according to claim 12, comprising impressing a certain voltage on the motor in an unloaded state of the linear actuator, measuring the rotational speed of the spindle, then calculating the motor constant is on the basis of the formula Spindle speed=(motor terminal voltage−motor current*Rloss)*motor constant making the assumption that the motor current is zero. 14. The method according to claim 13, comprising loading the spindle nut with a known load, impressing a certain known voltage on the motor, and measuring the motor current, then calculating the electric loss Rloss of the motor on the basis of the formula Spindle speed=(motor terminal voltage−motor current*Rloss)*motor constant applying the motor constant. 15. The method according to claim 12, comprising calculating the motor current based on the voltage V2 over a small series resistance Rm in series with the motor. 16. The method according to claim 11, comprising recording a certain length of travel of the spindle nut, recording the corresponding time of travel and the voltage impressed on the motor, then calculating the electromotive force on the basis of the formula: EMF=time*motor terminal voltage. 17. The method according to claim 16, comprising calculating the position of the spindle nut at any time on the basis of Position=EMF*motor constant. 18. The method according to claim 17, comprising calculating the position of the spindle nut every millisecond based on the known position of the spindle nut on the spindle. 19. The method according to claim 18, comprising storing the position of the spindle nut in a memory. 20. The method according to claim 18, comprising calibrating the position of the spindle nut every time the spindle nut reaches a known position on the spindle. 21. The method according to claim 19, comprising locating known positions, so that the spindle nut during normal operation of the linear actuator from time-to-time pass at least one known position.
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