Computer interference in our daily lives is becoming increasingly noticeable, how does the computer system in cars work? Next, the computer system inside your car... how it works
A labyrinth of wires and computers is the key to your car's deepest secrets. A Control Area Network, or CAN, is incredibly complex, but here's what drivers should know about how to keep your vehicle's components connected. In the following article, we will review the computer system inside your car... how it works.
The computer system in cars
Lots of questions have been asked about car parts that squeak, vibrate and break. But for some time now we have been seeing some questions about electronic component failures. So let's talk about a little-discussed feature of your car: its network of computers. In the past, we used to call it the electrical system, but its mission has evolved in a way that goes beyond just moving electrons. These electronics are collectively known as a Control Area Network, or CAN, but specifically, the system of wiring and software protocols that act as connective tissue between a vehicle's computers and sensors is known as CANbus. It could allow cars to be smarter, cheaper, and capable of doing some pretty cool things that wouldn't otherwise be possible.
Information infrastructure
Eric Button, the technical specialist at Ford, said about the intricacies of the automotive computer system. "While getting into a car, Button advises drivers to be aware that everything may appear straightforward but is actually highly complicated. The design of CAN is similar to that of the highway system. Data travels like vehicles from high-traffic highways to local roads across ramps, on and off ramps. Thousands of data points traverse this highway at any time along any given stretch and can get off at any exit. Throughout the car are different computers called ECUs - traffic lights and junctions for our analogy to a road system - each ECU has several functions:
- Engine or transmission control.
- Roll up the windows.
- Open doors to other functions.
These computers have sensors and switches wired to detect variables such as temperature, pressure, voltage, acceleration at different angles, braking, yaw, vehicle roll, steering angle, and many other signals. When the ECU needs a signal from a sensor connected to an ECU elsewhere in the vehicle, this is where the CAN function comes in.
Like a highway, the CANbus network allows data from all sensors and computers to travel around the vehicle at all times. Each computer is constantly transmitting all of its sensors and programming information up to 2,000 signals floating around the network at any time whether they are ordered or not. At the same time, each ECU "listens" to the network to extract bits of information it may need to do its job. There is no central hub or steering system, just a continuous flow of information always available to the ECUs.
Close the sliding doors
Take, for example, power sliding doors, which are a common feature of modern minivans. These doors are operated by an electronic control unit called a body control unit. Sensors report whether a door is open or closed, and when the driver presses a button to close the door, the signal from that switch is broadcast over the network. When the ECU receives this signal, it simply does not close the door. First, it checks the data stream to make sure the car is parked and not moving. If all is well, it gives a command to an electrical circuit that activates the actuators used to close the door. It goes further - the ECU then monitors the voltage being consumed by the motors - if it detects a voltage spike, which occurs when the door is obstructed by a stray handbag or body part, the ECU immediately reverses the door to prevent potential injury. If the door is closed properly, the latch locks the door electrically. This would have been a technical achievement in the past. Simply powering the doors required dedicated wiring running between the transmission, the door switch, and the motor.
Prior to the development of CAN in the mid-1980s, every time an automaker added an electronic feature, such as heated seats, new custom wires had to be added just to connect the heaters to a dash-mounted switch. Over the years, more features meant more wires, until there were literally miles of wires in wrist-thick chrome wrapping all over the car. With CAN, seat heaters and the powered switch do not need to be connected directly together. They can simply "communicate" over an existing CAN network - no special wires required - however, some additional programming is required to connect all devices to the network. It is a choice to shift towards programming complexity rather than physical complexity. Computer systems can make software development more difficult, but it has had many positive effects, most notably:
- Significant cost savings for the consumer.
- Much lighter weight.
- Reducing dependence on rubber and copper resources.
- Much better reliable with fewer wires to break over time.
These features may be important from a technical point of view, but the most profound impact of this shift toward programming is on vehicle diagnostics and software updates.
More development in the world of computer systems
Reducing car wiring harnesses and other advantages were not the main motivation for creating CAN. As pollution requirements matured in the late 1970s, the National Highway Traffic Safety Administration and the California Air Resources Board called for ways to monitor the effectiveness of vehicle emissions control systems. The result of this directive was the Unified On-Board Diagnostic Protocol (now in its second generation, known as OBD-II) which required the CAN network to efficiently communicate with all engine sensors for self-diagnosis. With this interconnection, the designated ECU can watch the network to broadcast trouble reports to the network as OBD-II codes. The check engine light comes on if the ECU discovers a fault and communicates it as an alphanumeric code. Modern cars perform these self-checks any time the vehicle is in operation. Anyone with a portable code reader can plug into the standard 16-pin data port in the driver's foot and retrieve fault codes. An internet search will usually explain the error or at least give a hint about the problem.
The same data port is also useful if the manufacturer detects a computer malfunction or wants to modify how the vehicle operates. For example, a car manufacturer might develop an algorithm for smoother transmission shifts. Installing it in any customer vehicle is as simple as a dealer technician plugging their computer into the data port and downloading the new software. Before CAN, this meant physically replacing the ECU.