Method for measuring current in a pulse count positioning system

#The present invention relates generally to pulse count positioning systems and more particularly to a method of measuring current levels and pulses that correspond with positions of an electric device such as an automotive accessory.

#The position of electric devices such as motorized automotive accessories for climate control air handling, seat positioning, mirror positioning, and sunroof operation, among others, is generally controlled by an electric motor in communication with the electric device. Often, the position of the electric device must be known in order to facilitate certain features such as seat memory or safety functions such as stopping and/or reversing movement of a power sunroof when an obstruction is present. Methods of determining the position of the electric device include individual potentiometers mounted to the electric device that generate an electrical signal corresponding with position information, or more prevalently, pulse count positioning systems that count commutation pulses of the electric motor.

#Pulse count positioning systems are well known in the art and generally determine the position of an electric device, e.g., automotive accessory, by counting the number of commutation pulses generated by the electric motor powering the device. As the electric motor rotates, current through motor windings is periodically interrupted as motor brushes rotate between poles of the motor. As a result, pulses or spikes in the current are produced, which are commonly referred to in the art as commutation pulses. Since the electric motor has a fixed number of poles, and each revolution of the motor causes the device to move a known distance, the position of the device may be correlated to the number of commutation pulses generated by the motor. Accordingly, the position of a device may be determined without the need for additional components such potentiometers or switches as previously implemented in the known art.

#The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

#FIG. 1 is a block diagram schematic of a pulse count positioning system in accordance with the principles of the present invention;

#FIG. 2 is a block diagram schematic of a signal processing system in accordance with the principles of the present invention; and

#The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

#Referring to the drawings, a pulse count positioning system in which the methods of the present invention are employed is illustrated and generally indicated by reference numeral 10 in FIG. 1. As shown, the pulse count position system 10 comprises a signal processing system 12 that receives a current pulse signal from a DC motor 14, an analog to digital (A/D) converter 16 that converts an analog current signal to a digital current signal and measures the current at regular intervals, a microcontroller 18 that receives the digital current signal and sums the current at the same interval as the A/D converter 16 or at least before the next interval occurs, and a timer 20 within the microcontroller 18 that is used to set a time for the regular intervals as described in greater detail below. As further shown, the microcontroller 18 is in communication with a communications system 22, which generally transmits information to the host microcontroller 24 on how an actuator for positioning a device should be positioned based on the current measurements.

#As further shown, the microcontroller 18 is in communication with the DC motor 14 such that the DC motor 14 may be controlled based on the current measurement and processing methods in accordance with the present invention. Accordingly, the signal processing system 12, as illustrated in greater detail in FIG. 2, further comprises a current sensor 26, a pre-filter 28, a bandpass filter 30, and a detector 32, through which the current pulse signal is processed and transmitted to the timer 20 within the microcontroller 18. Further, the signal processing system 12 comprises an amplifier 34, through which the current pulse signal is transmitted to the A/D converter 16, which is preferably 8-bit in one form of the present invention.