Real Word Feedback/Control Systems

In our everyday lives we encounter a plethora of feedback/control systems. In this blog post, I will examine four of such everyday systems that we experience while on the road.

Pedestrian Crosswalks

According to the CDC(the Center of Disease Control and Prevention), in 2013, 4,735 pedestrians were killed in traffic accidents in the US. Many of these accidents took place during the evening when it's harder for drivers to see pedestrians at crosswalks. This feedback and control system, which has been implemented in a few cities, can help to seriously decrease these numbers.

Either a force sensor is placed underneath the crosswalk or a push button is placed on a nearby lamppost. The sensing mechanism, force sensor or push button, then relays a message to the control center. This is probably done with some form of circuitry. When the computer/program registers that there is a person waiting to cross the street, the lights around the crosswalk and on nearby posts will light up and flash to inform drivers that a person is crossing, the actuator part of the system. In the case of using a force sensor, the system is intelligent enough to decipher the difference between a bird landing on the crosswalk versus a human being.

This simple feedback and control system is a really helpful way to decrease the number of pedestrian related incidents. In addition, as you can see in the above photo, this process is powered by solar power and hence is self sustainable and doesn't need additional power from a power grid. I think the whole design and concept of this system is really intelligent. Especially in the case of the force sensor, this system makes crossing the street especially safer for children, the elderly, and those handicapped in any way.

Traffic Light Sensors

This feedback and control system works similarly to the one above. This system is especially noticeable in the early morning of cities roads, at three way intersections, or at long stretches of road in order to control the speed of cars. This system does a really good job of easing possible traffic congestion. It works by using a force sensor placed before the crosswalk. In this way, the control center of the system is able to recognize that a car has stopped at an intersection.

The control  computation of this system is intelligent enough that is able to recognize the difference between a person standing in the middle of the street versus a car. This does beg the question of whether the sensor will be able to register a bicyclist... Once the system has registered that there is a car waiting at the intersection, the traffic signal will then turn green allowing the car to go through the intersection. If there is no car, the traffic signal usually defaults to red for the smaller road.

How specifically this system works depends on the specific scenario. As I stated earlier this sort of system is easily application in many traffic light intersections/stretches of road.

In the case of a long stretch of road, the light turns to red if it doesn't sense a car before a certain determined amount of time. This then also forces cars to slow down their speed because they are forced to stop every so often when they otherwise wouldn't need to.

In the case of a smaller road intersecting a larger street, this sort of light system helps to ease traffic congestion, by minimizing the amount of time cars on the larger road have to stop at a red light. If there's rarely any cars coming out of that intersection, why cause a delay on the larger street for no reason.

Lamps on the Side of the Road

The many lamps on campus and those on the side of the road are off during the day on turn on at night. Usually these lamps will have a light sensor, in the form of a photo resistor, on top of them that determine when it is dark enough outside for the lamp to turn on. This photo resistor is usually placed inside a simple circuit with a relay that toggles the light on or off depending on the light level.

We know however, how common it is for a lamp to not work properly. This error, the lamp begin on during the day or not turning on at night is usually an issue with a malfunctioning light sensor or a burned out bulb.

However, the simplicity of this circuit means it is pretty easy to maintain and relatively low cost. This is far more efficient than having a time based lamp as sunset/sunrise changes day by day.


Collision Avoidance Systems

To finish off our theme of feedback and control systems on the road, let's look at the collision avoidance system in cars.

This system usually uses radars, and sometimes lasers and cameras, to determine how far the car is from anything in front of/near it (e.g. a person,  another car, etc.). If the radar returns data suggesting something is too close, the system will then provide a warning to the driver, usually in the form of beeping, and either automatically brakes the car and/or steers the car. Which of the later the system does, depends on the speed of the car. If the car is too close and driving too fast to break in time, the system will then swerve.

In a study 2016 by the Insurance Institute for Highway Safety, the IIHS found that automatic braking systems reduced rear-end crashes by about 40%. That's a pretty significant number. However, this sort of technology is still relatively new and as a result hasn't been perfected. As such, it would be unwise to rely heavily on these systems. Further, I'm not sure whether the system will be able to tell the difference between a box on the road and a rolling ball that a child is chasing after. I'm sure that with further technological advances, collision avoidance systems have the potential of being extremely reliable and something self driving cars will rely heavily on.

Here are a few car commercials advertising emergency warning/brake systems: