Chapter 11 Flashcards
1) Compare how fatality rates for miles traveled have been reduced.
In the mid-1960s, safety belts became mandatory equipment in new vehicles
the fatality rate per 100 million miles traveled was 5.5 in 1966, 1.10 in 2011, 1.25 in 2016. The fatality rate would have been less, except for the fact that some people still do not use their safety belts or are doing something very unwise like texting or drinking while driving. The biggest cause of fatalities is driver inattention. By some estimates as many as 95 percent of all accidents are caused by driver inattention.
2) Explain what brought on the development of ABS braking and why.
Traction control systems are also discussed in this chapter because they basically use the same components as the ABS. Traction control applies the brakes to prevent a wheel from spinning on a low-traction surface. Traction control is almost the opposite of ABS. ABS stops a wheel from locking up, and traction control prevents a wheel from spinning. The addition of traction control came early in the development of electronic braking systems because only the addition of two valves and a pump and software changes made it operational on an existing ABS system.
3) Explain how the rear wheels were controlled on the original rear-wheel antilock brakes such as RWAL or RABS.
One of the most difficult vehicles to design a braking system for was the light truck. A manufacturer had no way of knowing how or even if the vehicle would be loaded. The first attempts at a solution was the height-sensing proportioning valve, followed by rear wheel antilock braking. This was the first true mass-production ABS installed on vehicles. The RWAL/RABS system was first installed on minivans and pickup trucks in late 1987. RWAL means rear-wheel antilock and is the most common term used by most manufacturers. RABS means rear antilock brake system and is the term commonly used by older Fords and some other manufacturers. The system essentially controls wheel skid only on the rear wheels. Usually the speed sensor was located on the differential housing and measured the speed of the differential ring gear.
4) Explain the difference between three- and four-channel ABS brakes.
In three channel ABS the front wheels are controlled independently, and the back tires are controlled as a pair
In four channel ABS every wheel can be controlled independently.
The next major development of the ABS system was the advent of three-channel and four-channel ABSs. Three-channel ABSs were the most common when ABS were first introduced in passenger cars. Both front wheels were controlled independently of each other, but the rear wheels were controlled as a pair. If one rear wheel started to lock up, then both rear wheels were modulated in the same manner. Finally, for stability control, four-channel ABS is the rule. All four wheels are controlled independently. ABS, as you recall, does not necessarily stop a vehicle faster but allows for control of the vehicle in a hard-braking situation. If the front wheels lock, the vehicle cannot be steered; if the rear wheels lock, then the vehicle tends to spin out of control
5) Explain what is meant by understeer.
Understeer, simply stated, means that the vehicle did not make it through a turn and went off the road on the outside of the turn. It appears almost as though the driver did not turn hard enough, but more than likely was driving too fast for weather conditions or the condition of the tires or vehicle and the front wheels lost traction (Figure 11-11). In an understeer situation, the inside rear-wheel brake can be applied by the stability control system to help pull the vehicle around the curve.
6) Explain what is meant by the term oversteer.
Oversteer is the loss of traction at the rear wheels leading to a vehicle spin (Figure 11-12). Once again, the driver might have steered into the corner too hard, the rear tires might
7) Describe the first response to wheel slip by the traction control.
if the EBCM senses wheel slip when the brakes are not applied, its first step is to request the PCM to reduce engine torque.
8) Explain how computer-controlled hydraulic steering works.
Electronic or electrically controlled steering began in the 1990s. The electric steering computer regulated the flow of pressurized power fluid to the steering gear. During lowspeed operation, full power steering flow was allowed for parking maneuvers. At highway speeds the power steering flow is cut back for better road feel. Full power steering pressure can be delivered during an emergency maneuver by utilizing the steering wheel angle sensor. The steering angle sensor for one of these hydraulic systems is located at the bottom of the steering column and measures steering rotation in both degree of turn and speed of steering wheel rotation (Figure 11-3). Using these data and other information such as VSS, the electric steering computer regulates the flow of pressurized power fluid to the steering gear using a solenoid mounted on the power steering pump (Figure 11-4). Other electrical steering assist can be done by attaching an electric motor to the steering shaft or gear that can apply force to the steering mechanism
9) Briefly explain how active braking systems operate.
Active braking systems will build increased pressure from the master cylinder in anticipation of a panic stop, when the danger of an impending crash is possible as measured by the vehicle’s short-range radar system
10) Explain the use of a yaw sensor.
The yaw sensor can measure the difference between the actual direction that the vehicle is traveling and the direction the driver is trying to steer the vehicle by way of the steering angle sensor. This difference is called the slip angle. The VSC computer then calculates the amount of steering correction needed.
- By some estimates, as many as _______________ percent of all accidents are caused by driver inattention.
95%
- Computer _______________ inside the vehicle allowed the ECM, BCM, ABS, and stability control (VSC) modules to react as one to prevent crashes.
(not sure of this answer)
- Traction control is basically the _______________ of ABS.
Reverse
- The _______________ sensor is a dual sensor that is mounted on a torsion bar inside the steering column.
Torque
- The Toyota Prius uses _______________ braking that begins as soon as the accelerator pedal is released by activating the motor/generator.
regenerative
