It has happened to every driver at one point or another. You are driving down the highway with the windows down enjoying the music coming from the radio. Your mind drifts to the fun times you had while listening to that same song, maybe it was a previous vacation or even the awkwardness that was middle school, either way your mind is wondering, not quite aware of your surroundings. But then you hear it, the loud whirring that all drivers dread, you quickly look in the rear view mirror and sure enough you see the flashing red and blue. You then look at the speed-o-meter, shoot, you can’t remember what the speed limit is, but you are rather certain 95 mph is not it.
But it does not have to be like that, there is a magical system that when used properly guarantees the speed will be obeyed, even when you are more focused on nostalgia and less on the gas pedal.
Cruise control is an option that many cars are equipped with today. The usage of cruise control in today’s world depends on the driver and the car. Therefore, while cruise control is not necessary to the functionality of the car, it does make lengthy, tedious road trips more manageable. In addition, cruise control ensures that you stay at the speed limit. It can definitely save some one from getting a ticket or two by ensuring that the driver does not run above the speed limit, making it a valuable entity.
The main purpose of process control is to minimize the effect of the unexpected and to maximize the efficiency of the expected. When it comes to the system of cruise control in a car, the expected would be the function of having the car navigate at a constant speed set point without having the user to press on gas. The unexpected would be when the system does not function properly due to disturbance variables that affect the speed of the car. The controlled variable in this system would be the speed of the car. If the speed of the car matches the input speed, the system is functioning as desired. If the speed of the car is not reaching the set point, this means that there are perturbations present in the system. These perturbations could arise from the various disturbance variables. Disturbance variables can include changes in the road, such as hills or the composition of the gravel. They can also include weather conditions, traction, tires, car malfunctions, such as leaking gas and oil, or even a broken belt or fan. When these disturbances occur, the system can correct them via a feedback controller.
The feedback controller measures the output speed of the car using a sensor and then sends signals back to the controller, which can increase the work done by the system, adjusting the speed as necessary. Unfortunately, unexpected disturbances can cause accidents if the environment of the car is not suitable for the speed of the car. For example: when driving in rain, the car may hydroplane, which would cause the overall speed of the vehicle to seem less when measured by the sensor. With cruise control, the sensor would determine that the speed has decreased and attempt to increase the work needed to make up for the loss of speed. The system would put the work to make the tires spin faster. Since tires do not have decent traction in rainy weather, the increase in tire rotation would cause accidental dilemmas that are not accounted for with the use of cruise control. In addition, the feedback controller would not be able to fix any issues within the car that could cause a change in speed. For example: if there is a gas leak in the engine, this would go unnoticed by the sensor from the cruise control in system. If the output of the car decreases due to this error, the cruise control sensor would not realize that it is due to the gas leak, and this could cause for more work to be put towards increasing the speed of the car. It cannot fix any other parts. This is where the process could be inefficient since the feedback control is only measuring the output speed and changing the work done by the engine based on the sensor measuring the output.
The manipulated variable of a cruise control process would be the input of the velocity. It is easy to determine the speed one wants since speed limits are usually given every few hundred feet along the highway. It is important to note that one can get achieve the set point that is desired without a cruise control system. However, the purpose of cruise control is to facilitate this process on the driver and to allow the driver to be able to focus more on the road rather than the speed at which he or she is driving at. The manipulated variable can be input into the system using the cruise control buttons, usually found on the steering wheel to make the ease of access easy and safe while driving. A video demonstrating this process on a 2015 Volkswagen Golf SportWagen is provided below.
From the figure above, one can see the feedback control system that is established for a cruise control system. The feedback occurs when a sensor registers the speed that the car is exhibiting and that information is then transmitted back to the controller of the system. From there, the controller can decide what the next action of the system will be and will send that information to the actuator. The actuator will allow the throttle and engine to put more or less work into the system to allow for the gears and wheels to be adjusted and for the system to accommodate for a new speed output. These changes are due to pressure changes from the actuator. Human interface is a part of the cruise control since the driver needs to decide what the set point of the system or speed of the car should be. This can occur with the choice of the various options available (on/off, set/decelerate, resume/accelerate, and cancel) in a cruise control operating system in a car.
As one can see, the cruise control system has revolutionized the car industry in recent years. Drivers do not have to worry about running above the speed limit since there is an option to control the speed of their control. Obviously, the driver can still choose to accelerate if he or she wants to but the cruise control system is available to help. By allowing drivers to focus more on the road rather than the speed of their car, the roads are safer. As technology improves, there are other feedback systems that have been designed to not crash into other vehicles, to monitor the distance between other cars, and to park with the use of cameras guiding one into the spot. Future roads will only become safer as time goes on.
Works Cited
Astrom, Karl Johan. “Review: Feedback Systems: An Introduction for Scientists and Engineers.” The Quarterly Review of Biology 83.4 (2006): 1-387. California Institute of Technology, 16 Sept. 2006. Web.