Parking sensors are devices we use every day. But how do parking sensors work? And what other systems are active every time you point in reverse? We found out.
From Justluxe Content Partner CarExpert
It’s something you take for granted. Every time you jump in the car, choose to go back and forth out of the lane, there are a set of systems that work to make sure not to return to anything or anyone else.
These systems have now evolved to accommodate the front and rear corners, along with attention to rear traffic when reversing. There are even systems that will remember the latest steering inputs to help reverse confined spaces.
We wanted to shoot a video explaining how the major parking systems used in cars today work. While there are small differences between cars on the market, most parking systems use the same basic equipment as a base – i.e. ultrasonic or electromagnetic parking sensors, radars and cameras.
To cover the full range of parking technologies, we use the Kia Sorento GT-Line and the BMW X5. These cars have technology that covers everything from reverse parking to remote parking.
How do ultrasonic parking sensors work?
Most of the new cars on the market today come with a combination of front, rear and side ultrasonic parking sensors.
You can tell if these are suitable for your vehicle by looking for small circuits built into your front, rear, or side bumpers.
They are usually the color of the body but can be another color and are usually evenly spaced.
Ultrasonic parking sensors work by emitting a high-frequency sound wave (like a high frequency so that the human ear cannot hear it), which collides with an object and is then reflected back into the vehicle. The amount of time it takes for the sound wave to return to the vehicle is then used to calculate the distance between the parking sensor and the object.
For all the tech geeks out there, the formula is distance = 0.5 * time * speed of sound. Since the speed of sound varies depending on temperature and humidity, the car has an inbuilt temperature sensor that changes the speed of counting the sound to ensure accuracy when it comes to parking.
However, there are some downsides to ultrasonic parking sensors. The sound waves are absorbed by things like clothing and human flesh. Sound waves can also be deflected in other directions by things like round-faced metal poles.
This is why cars use multiple parking sensors. They exist to repeat and confirm distances in the event that sound waves are deflected or absorbed by some organism.
Ultrasonic parking sensors have an effective range of only 3 to 5 meters, which makes them ineffective for long distance detection.
How do electromagnetic parking sensors work?
Electromagnetic parking sensors, such as ultrasonic parking sensors, act by emitting a wave and then timing its return. But there are some major differences.
Visually, it will not detect the electromagnetic parking sensors because they are generally placed behind the shock absorber and hidden from view. They appear as plastic tape with adhesive and are more popular in aftermarket.
Instead of emitting a sound wave, electromagnetic sensors emit a radio wave. The radio wave bounces off an object and then returns back to the sensor – the change in frequency is used to calculate the distance from the sensor to the object.
While electromagnetic sensors provide a greater field of detection compared to ultrasonic sensors, they are compromised by the fact that they only detect objects when the vehicle is in motion.
This means that you may experience interruptions and inaccuracies if there is an object moving between your car, stopping, and then moving again.
How does the 360 ° camera view or the bird’s eye camera work?
Parking sensors are easy to use, but relying on sensors as the only method of parking may not always be effective.
Having a visual indication of the vehicle’s surroundings helps detect anything that has been missed by the parking sensors.
We’ve seen reverse vision cameras used extensively in new cars, but car brands have taken it up a notch by incorporating additional cameras into the mix.
The 360-degree camera (also known as a bird’s eye camera) uses cameras mounted at the back, sides, and front of the vehicle to link an image that appears together to provide a view from the top of the vehicle looking down.
Instead of using cameras over the vehicle, the vehicle uses ultra-wide angle cameras and the image of each camera is grouped together to create the illusion of a bird’s eye view over the vehicle.
The quality of these cameras varies greatly across the sector. Some of them are of high quality and added value, while others are of low quality and quite granular, which makes them difficult to use and useless effectively.
On some vehicles, these cameras are activated automatically at low speeds when approaching objects to make parking easier.
How does the Rear Cross Traffic Alert work?
Rear Cross Traffic Alert is a technology capable of alerting the driver, and in some cases even braking the vehicle, in the event of a possible collision by a vehicle, cyclist or pedestrian approaching the vehicle if it continues to reverse.
The same technology is also installed on the front of some cars, with warning and braking applied when the vehicle is about to leave the parking spot in oncoming traffic.
We know that ultrasonic parking sensors have an effective range of only 3 to 5 meters, so vehicles with this technology use radar to help detect vehicles.
Radars are installed on the corners of the rear bumper (and the corners of the front fenders in cars with forward-facing versions of this technology) and are tilted to indicate cross-country traffic.
In a similar fashion to electromagnetic parking sensors, a radio wave is emitted at a certain frequency before returning to the vehicle. Once it returns, the frequency change is measured to determine the distance.
When a cyclist, vehicle, or pedestrian approaches the rear of the vehicle while reversing, the radar detects the change in the distance drop, notifies the driver with a warning and then applies another brake if the collision is imminent.
Other parking technologies
Other parking technologies you may have heard about stem from the technologies described above. Each of these systems uses one or more technologies to create new derivations of parking technologies that help drivers every day.
Remote parking technology
Tesla was one of the first manufacturers to launch the remote parking feature they dubbed the Summon brand. The recall allows the driver to move the vehicle forward and backward from outside the vehicle.
This technology has developed by other brands where the car can be moved using the key from the outside and recently Tesla has developed it further with Smart Summon, which allows the car to be driven independently inside the parking lot for the driver.
Depending on the vehicle, the vehicle uses a combination of parking sensors, radar, and camera technology to move the vehicle in the direction the driver instructs.
A signal from the driver directs the car, stops and starts moving. The switch (or your phone) acts as a deadman switch, effectively stopping the vehicle immediately upon releasing the button.
Emergency self-braking is common in most new cars today and works by stopping the vehicle if a collision is imminent and the driver does not react.
Reverse AEB uses ultrasonic parking sensors to detect objects in the back of the vehicle and in the event that the driver has not stopped and a collision is imminent, the vehicle will suddenly brake to prevent a collision.
Just like all of these systems, there are limitations to how well they work and the onus is always on the driver to make sure they keep an eye out for the space behind the vehicle.
Parking in parallel and vertical is independent
Semi-autonomous parallel and vertical parking uses a combination of ultrasonic parking sensors and electric motor-driven steering to guide the vehicle to the parking lot.
The algorithms in the vehicle’s ECU either measure the size of the parking lot continuously or on demand to determine if the bay can fit your vehicle. With a predefined set of dimensions, if your vehicle detects that it can fit into the cabin, it provides this information to the driver and waits for a command to start the process.
Once the process begins, the vehicle will begin the process of reversing into the park (either parallel or perpendicular) and moving the steering wheel on its own. This system only works on cars with electrically assisted steering racks and not on cars with the older hydraulic type.
During operation, the driver remains ready near the brake pedal to stop the vehicle if the operation does not work as it should.
Some cars, like the BMW X5, will also physically change gears, so all a driver needs is to watch.
Some vehicles also offer the ability to get help leaving the park as well. So once the car is parked, pressing the right button starts the process of moving the car back and forth with enough steering lock to leave the parking lot.
It works the same way it does when entering a park. Pre-set steering geometry and inter-vehicle spacing allow the vehicle’s ECU to calculate correct steering motions to maneuver out of a parking spot.
The last piece of technology we’ll cover is the BMW Reverse Assistant. Although it is currently only available in BMW cars, we doubt it will eventually be offered by other brands.
BMW cars with this technology remember the last 50 meters of steering inputs and allow the driver to recycle these steering inputs in the opposite direction.
What is the point of this? If you find yourself on a narrow one-way street and discover that you need to turn back, pressing the Reverse Assistant button will take care of it for you. It takes the pressure off the need to avoid barriers and other cars when reversing.
It uses a combination of the aforementioned parking sensor technology, together with the steering input memory, to reproduce the last 50 meters of the steering input.