The system control of THS II maintains the vehicle at its maximum operating efficiency by managing the energy used by the entire vehicle, which includes the energy for moving the vehicle as well as the energy used for auxiliary devices, such as the air-conditioner, heaters, headlights and navigation system. The system control monitors the requirements and operating states of hybrid system components, such as the engine, which is the source of energy for the entire hybrid vehicle; the generator, which acts as the starter for the engine and converts the energy from the engine into electricity; the motor, which generates the drive power for running the vehicle using the electrical energy from the battery; and the battery, which stores the electrical energy generated through power generation by the motor during deceleration. It also receives braking information being sent via the vehicle's control network, as well as instructions from the driver, such as the throttle opening and shift lever position.
In other words, the system control of THS II monitors these various energy consumption statuses of the vehicle in real time and provides precise and fast integrated control so that the vehicle can be operated safely and comfortably at the highest possible efficiency. Like modern jet planes, THS II hybrid vehicles use by-wire control, in which the driver's instructions are converted into electrical signals (through wires) to be used in integrated control. In by-wire control, system reliability is the highest control priority. When a smart key sends information indicating that the driver has gotten inside the vehicle, the system power supply is turned on. First, whether or not the hybrid computer itself is functioning normally is monitored, and an operational check is performed before the ignition button is pressed. When the ignition button is pressed, the system checks whether or not various sensors, the engine, the motor, the generator and the battery are functioning normally.
Then, the switches for the components in the high-voltage system, such as the motor, the generator and the battery, are turned on, making the vehicle ready to run. This is the start-up control sequence. When the driver presses the ignition button again before leaving the vehicle, the components in the high-voltage system are disconnected and, after confirming that such systems are turned off, the hybrid computer shuts down.
Safety checks are also being carried out while the vehicle is moving, and, based on various types of information such as changes in driving conditions, the system controls the vehicle so that it can operate in an emergency mode in the unlikely event of failure in the hybrid system or lack of fuel. Engine power control is the basic control mechanism of THS II for always minimizing the energy consumption of the entire vehicle. Based on the vehicle's operating state, how far the driver has depressed the acceleration pedal and the status signals from the battery computer, energy management control determines whether to stop the engine and run the vehicle using the electric motor only or to start the engine and run the vehicle using engine power. When first started, the vehicle begins to operate using the motor unless the temperature is low or the battery charge is low. To run the vehicle using engine power, the engine is first started by the generator and at the same time, the system calculates the energy required by the entire vehicle.
It then calculates the running condition that will produce the highest efficiency for producing this energy and sends an rpm instruction to the engine. The generator then controls the engine revolution to that rpm. The power from the engine is controlled by taking into account the direct driving power, the motor driving power from electrical generation, the power needed by the auxiliary equipment and the charging requirement of the battery. By optimizing this engine power control, THS II has advanced energy management for the entire vehicle and has achieved improved fuel efficiency.
The driving power of a vehicle with THS II is expressed as the combination of the direct engine driving power and the motor's driving power. The slower the vehicle's speed, the more the maximum driving power is derived from the motor's driving power. By increasing the generator rpm, THS II has made it possible to use the engine's maximum power starting at slower speeds than was possible with the current THS. It has also made it possible to significantly increase the maximum drive power by using a high-voltage, high-output motor that successfully improves power performance. Because the engine has no transmission and uses a combination of the direct driving power from the engine and the motor's driving power derived from electrical conversion, it can control the driving power by seamlessly responding to the driver's requirements, all the way from low to high speeds and from cruising with a low power requirement to full-throttle acceleration.
(This is known as torque-on-demand.) Additionally, the time required to start the engine during acceleration from motor-only drive has been reduced by 40%, greatly improving the acceleration response. In order to eliminate shock during engine start-up, the generator also precisely controls the stopping position of the engine's crank. To ensure that the vehicle's driving power is not affected even when a large load is applied, e.g.
, when the air-conditioner is turned on, precise driving power correction control is carried out, achieving smooth and seamless driving performance. In THS II, the newly developed Electronically Controlled Braking System (ECB) controls the coordination between the hydraulic brake of the ECB and the regenerative brake and preferentially uses the regenerative brake; it also uses a high-output battery and increases the amount of energy that can be recovered and the range in which it can be recovered. The system increases overall efficiency and, thus, fuel economy. In THS, the engine, the generator, the motor and the wheels are linked together via the power split device. Furthermore, most of the engine power is converted into electrical energy by the generator, and the high-output and high-response motor drive the vehicle. Consequently, when the vehicle's driving power changes abruptly, e.
g., wheel slippage on icy or other slippery surfaces and wheel locking during braking, a protection control similar to that used in conventional traction control is used to prevent abrupt voltage fluctuation and revolution increase of the planetary gear in the power split device. In THS II, we have advanced the parts protection function further and achieved the world's first motor traction control by utilizing the characteristics of a high-output, high-response motor. The goal of the motor traction control is to restore traction when wheel slippage on a snowy road is detected, for example, and inform the driver of the slipping situation. The basic requirement for safe vehicle operation is firm traction between the tires and the road surface.
Motor traction control helps the driver maintain this state. This is another driver assist function that is unique to the high-output motor THS II. This function prevents the vehicle from sliding downward when the brake is released during startup on a steep slope.
Because the motor has a highly sensitive revolution sensor, it responsively senses the angle of the slope and the vehicle's descent and ensures safety by increasing the motor's torque.
Melih ("may-lee") Oztalay, CEO SmartFinds Internet Marketing Web: www.toyotaofbedford.com EMail: melih@hsfideas.com Toyota Ohio state customers now have an online showroom built with Toyota Cleveland Ohio shoppers in mind.
