Study Of Control For Double Motors Wiper System Based On Differential Flatness

Electron technology is more and more widely used to equip vehicles in recent years, with the continuous development of electronic industry and automobile industry. Traditional mechanical windshield wipers are gradually replaced by windshield Wipers system driven by two motors. In two-motor wiper system, we have two independent motors driving the wiper arm on each side of the windshield without heavy connecting rods. The mechanism, which was used to connect the two wipers together, is completely taken off. As a result of that, noise and breakdown produced by the mechanism could be evidently reduced, and we could also save the power consumption as well as the space needed for the wiper system. In addition, we can place the wiper system more freely, because the limitation on distance or angle does not exist anymore.In this article, we introduce the basic conception of differential flatness. Then we talk about the two-degree-of-freedom controller based on the single side. First of all, we prove the system made up with a dc motor, a gear and a wiper was differential flatness. At this time we find that the angular position of the wiper could be the flat output. So, the exact trajectory of the state and control can be deduced from the trajectory of the angular position. The excepted trajectory of voltage applied on the motor can be used as a feed forward control variable. It could drive the system act as we hope exactly, if there is not any noise. But in reality, all kinds of noises and uncertainties can not be avoided. So we designed PID controller, as the back forward controller, to correct the error.To design the PID controller, we use the pole-placement to find the satisfyingparameters of the PID controller. But we find that this method depends on the exact model of object, which is always difficult to get in practice. So we use Z-N Oscillation method to calculate the PID gains. But most of the mechanical systems do not allow oscillation. So we make use of a more developed method which does not need the oscillation of the system.As we talk about the synchronization of the pair of wipers, we introduce the master reference control and the master slave control, which are used commonly in the process of manufacturing. We make use of master slave control in our system. The master follows the excepted trajectory as its reference, and the slave follows the output of the master. The roles of wipers, as the master or the slave, exchange according to the moving direction. When the master slows down its speed, the slave should have corresponding reaction to avoid collision. We find that this two wipers follow the same trajectory if there is no noise. They start to move at the same time and come back to their parking position together. Collision can not be avoided if the initial position is not very suitable. So we introduced another technique called"clock control". When the wipers move up, while leaving their parking position, the driver's wiper moves first, while passenger's one follows. Conversely, when going back to their parking position, the passenger's wiper is the leader and the driver's one the follower. Therefore, to avoid collisions when the leader is behind its reference trajectory, the"clock control"mechanism will delay the local clock of the follower's reference trajectory.Finally, the hardware and software are considered at the end the article. We talk about the entire frame of the hardware, the chose of power regulator, microcontroller, switch detection interface and motor driver. And we also illustrate the method we use to detect the motion of motor. We have two Hall sensors in each motor, which give out continuous square waves while the motor is running. And wecould get the information of the motion from the frequency and phrase of the square waves. In the software designing, we considered the main process, time scaling mechanism, the realization of PID controller and PWM producer.As we said before, each of the pair of the wipers is driven by its own independent motor. The synchronization of the wipers is obtained by clock control instead of traditional rigid mechanical coupling driven by a single constant speed motor, which has been removed here for the sake of weight and space. We are free to place this mechanism in the dashboard and we get wider wiped surface of screen.