The invention relates to a method and system for determining movement of a motor in a vehicle power window system for detecting an object caught between the window and its respective frame.
Many vehicles today have electronically controlled windows and electronically controlled sun/moon roofs. These systems provide the operator with ease in opening and closing the windows. However, if the operator is distracted while closing the window, it is possible for an object, such as an arm, hand or finger, to be caught between the window and the window frame of the automotive window.
Power window systems typically include a regulator attached to the window for opening and closing the window and driven by an electric drive motor. The motor current wave form of these windows has a distinct sinusoidal component caused by the commutation process. Each commutation pulse can be related to angular rotation of the motor armature. Thus, window position can be determined by counting the commutation pulses. However, a problem arises due to random error pulses mixed in with the commutation pulses thereby introducing error into the position count. The error pulses cannot be filtered out using conventional band pass filter techniques because the magnitude and frequency of these error pulses are within the frequency range of the commutation pulses.
Thus, there exists a need for accurately determining movement of the motor via a change in the position of the motor for determining the presence of an object caught between a power window and its respective frame.
A method and system is disclosed for determining movement of a motor in a vehicle power window system. A current sensor senses a current of the motor and generates an input signal having a phase associated therewith. A signal generator generates a voltage controlled reference signal having a predetermined phase and a frequency associated therewith. A comparator is in communication with the current sensor and the signal generator for comparing the phase of the input signal with the phase of the reference signal. A control circuit, in communication with the signal generator, determines whether there is any movement of the motor based on the comparison.
The comparator determines a difference between the phase of the input signal and the phase of the reference signal and passes this difference to the signal generator, which then adjusts the frequency of the reference signal based on this difference. A second comparator converts the adjusted reference signal into a digital signal having pulses so that the control circuit can count the number of pulses in the adjusted reference signal to determine the position of the motor. The control circuit also determines whether the position is changing. If the position does not change, this may be indicative of an obstruction.
A motor drive circuit that controls the power window system is controlled to either stop or reverse the direction of the motor if the position of the motor has not changed and is constant.
These and other features of the present invention can be understood from the following specification and drawings.