Reduces the automobile energy consumption and the reduced waste gas discharges is the most important question which now the automobile development must solve. The practice indicated that, is loaded with the metal belt type variator (an infinitely variable the automobile, its efficiency, the power and discharges is loaded with other automatic transmissions and the manual mechanical variable speed drive automobile is better than.

Regarding the metal belt type variator (an infinitely variable design, its core question is to its control system design.

The metal belt type variator (an infinitely variable control system main function is: Reliably transmits the driving gear the engine output, and as far as possible throttle closure loss; According to the automobile movement condition, the working pattern automatic change velocity ratio which designated according to the pilot, causes the engine to maintain at the ideal operating point. Therefore, variator (an infinitely variable (CVT) the control divides into according to its function clamps the strength control and 速比 the control. Clamps the strength to control to the transmission efficiency height plays the decision role, if clamps the strength excessively to be small, then the strap can in 带轮 on slip, this not only reduces the transmission efficiency, but also can speed up the strap and 带轮 attrition; Clamps the strength oversized, will increase the nonessential friction loss, similarly also will be able to reduce 传动�?efficiency. According to the automobile movement condition, only has clamps the strength control in the target value small scope, can effectively enhance 传动�?efficiency.

Take the metal belt type variator (an infinitely variable as the research object, clamped the strength control to it the method and the controller has separately conducted the research and the development, and has carried on the experimental confirmation.

Second, clamps the strength control valve the characteristic

In the engine work rotational speed scope, the test clamps the strength control valve when the different input rotational speed, its discharge pressure along with input signal change.

The solenoid valve input signal maintenance is invariable, when input rotational speed change, the survey clamps the strength control valve the discharge pressure. Attempts 1a is when differently occupies the spatial ratio, clamps the strength control valve the discharge pressure change curve. Attempts 1a to indicate that, under the identical rotational speed, occupies empties compared to the increase along with the input signal, the control valve adjustment pressure in the certain scope inside connection change, when occupies the spatial ratio is lower than some value, because the control valve has 死区 the existence, cannot adjust the pressure; When occupies empties compared to is higher than some value, the control valve adjustment ability achieves saturated, also does not play the role; Occupies empties when is same than, along with the rotational speed change, the control valve adjustment pressure also changes (to attempt 1b). This is as a result of along with the engine rotational speed increase, the oil pump displacement increase, thus causes the solenoid valve pressure control scope to change. When rotational speed lower, the oil pump displacement is small, the system produces increases slightly. System this kind of characteristic inevitably affects the actual control effect.

Also may see by chart 1, controls the solenoid valve the effective PWM signal to occupy empties compared to the scope and the input rotational speed related, when input rotational speed low, because the oil pump displacement is lower than clamps the strength control valve the fixed current capacity, therefore the solenoid valve adjustment scope is very narrow. Along with the input rotational speed increase, the oil pump current capacity increase, the solenoid valve adjustment scope widens. But works as when the input rotational speed is very high, because hydraulic system own divulging, the pressure cannot increase. Therefore, under the different rotational speed, controllably clamps the strength control valve the PWM signal to occupy empties compared to is different. Clamps the strength control valve steady-state characteristic output like chart 2 to show.

Third, clamps the strength controller the design

The stepless variable transmission clamps the strength control to be allowed to divide is two levels: First is the control system sets a target according to pilot's input and the outside travel condition clamps the strength, the target value outputs the implementing agency on the controller; Then the controller the actual value deviation which obtains according to the target value and the survey controls the implementing agency movement, enables the system the actual value to approach or to achieve the target value. Because control strategy and implementing agency related, therefore the controller design should consider the CVT system shifts gears the characteristic and the hydraulic control system (specially is control valve) characteristic.

Usually, in the metal belt type stepless variable transmission system, clamps the strength the target value is and 速比 the computation obtains according to the current transmission torque, then inputs to clamps in the strength control system. Therefore, clamps the strength control the goal is follows the goal pressure the change to change, therefore in order to enhance the hydraulic system the efficiency, 超调�?should as far as possible small, the system response time must be as far as possible short.
Because clamps the strength control valve existence integrator to wind around (or integrator function terminated) the phenomenon, therefore must take the measure to prevent the integrator function terminated, namely must cause to clamp the strength control valve throughout to work in the controllable scope, this obviously cannot use conventional the control method to solve. In in this control system design, uses has the forward feed anti- to wind around the PID controller to prevent the integrator winds around, like chart Shows, this system has provided an attachment forward feed channel. The controller survey implementing agency model output forms error signal es, es is implementing agency output mu c and the controller outputs v between the difference, and through increases this error 1/Tt to feed back the integrator. When the implementing agency has not been saturated, this error signal!" �?zero, when the implementing agency is saturated, the attachment feedback channel attempts to cause error signal es to be equal to zero. This meant the integrator repositions, causes the controller to output occupies the saturated limit. Thereupon the integrator (is called track time-constant) by time-constant Tt to reposition to a suitable value. The implementing agency model is in advance through the experiment definite mathematical model, its output may approximately regard as the actual implementing agency output the value. In order to reduce the system the over modulation, joins a forward feed channel. The forward feed channel joins can cause the controller the initial output to be very big, also can simplify the integral link the influence, makes the system the response to speed up. Only has works as error controller output control when in saturated nonlinear element linear sector, the integrator only then plays the role. Thus, the controller outputs description as follows:

Because clamps the strength control valve existence integrator to wind around (or integrator function terminated) the phenomenon, therefore must take the measure to prevent the integrator function terminated, namely must cause to clamp the strength control valve throughout to work in the controllable scope, this obviously cannot use conventional the control method to solve. In in this control system design, uses has the forward feed anti- to wind around the PID controller to prevent the integrator winds around, like chart Shows, this system has provided an attachment forward feed channel. The controller survey implementing agency model output forms error signal es, es is implementing agency output mu c and the controller outputs v between the difference, and through increases this error 1/Tt to feed back the integrator. When the implementing agency has not been saturated, this error signal!" �?zero, when the implementing agency is saturated, the attachment feedback channel attempts to cause error signal es to be equal to zero. This meant the integrator repositions, causes the controller to output occupies the saturated limit. Thereupon the integrator (is called track time-constant) by time-constant Tt to reposition to a suitable value. The implementing agency model is in advance through the experiment definite mathematical model, its output may approximately regard as the actual implementing agency output the value. In order to reduce the system the over modulation, joins a forward feed channel. The forward feed channel joins can cause the controller the initial output to be very big, also can simplify the integral link the influence, makes the system the response to speed up. Only has works as error controller output control when in saturated nonlinear element linear sector, the integrator only then plays the role. Thus, the controller outputs description as follows:

Clamps the strength control system diagram like chart according to the above theory establishment 4 to show. Because clamps the strength control valve the effective PWM signal to occupy empties compared to has the difference under the different rotational speed, therefore may effectively occupy the corresponding different rotational speed under spatially compares with a mathematical table, like this under the different rotational speed may through the interpolation determine the saturated limit occupies the spatial ratio. In view of clamps the strength control system design anti- to wind around the PID controller actual input to have the target value which the system establishes, to clamp the strength control valve the output feedback value and the current system input rotational speed. The controller first acts according to inputs the rotational speed to determine under this rotational speed clamps the strength control valve the saturated sector limit value, then carries on the control according to the target value and the system feedback deviation.

Fourth, clamps the strength control system model simulation and the experimental study

In order to confirm clamps the strength control model which discusses the accuracy and the reliability, to clamped the strength control system diagram design according to above to clamp the strength control model to carry on the simulation experiment, result like chart 5 has shown. When the goal clamps the strength to occur the step jumps, from the controller discharge pressure value change curve obviously, clamps the strength over modulation slightly, stable is quick, namely the controller can well the control action.

In order to further the research institute designs the control system actual control effect, will study CVT will clamp the strength control system and 速比 the control system composition CVT control system transplants to the automobile on, carried on the entire vehicle experiment, test result like chart 6 has shown.


By chart 6 obviously, in the t1 time, opens the under pick-up in the input certain damper, the engine speed along with it increase. The control system basis current input sets a target 速比, the output signal to clamps the strength control valve and 速比 the control valve, controls the host, the driven wheel cylinder pressure variation, actual makes 速比 to the goal 速比 change, the automobile speed to increase, in various parameters change like chart shows. In t2 time, after further increases the engine the damper to open (to attempt 6a), open the engine speed to should the damper to change, the corresponding goal 速比 changes, then the control system controls the host, the driven wheel cylinder pressure further changes (attempts 6d), enable actual 速比 速比 to approach to the goal (attempts 6c). The engine rotational speed and the automobile speed like attempts 6b to show, namely when the system achieved when stable state, actual 速比 速比 is consistent with the goal, the automobile vehicle speed no longer increases. In t3 time, after the running resistance suddenly increases, because the engine damper opens a maintenance invariablely, engine goal rotational speed invariable, the corresponding current travel operating mode goal 速比 changes, the control system through controls in the host, the driven 带轮 cylinder pressure, the control is actual 速比 to lowly keeps off the direction change.

The test result indicated that, this control system can appropriately defer to the travel operating mode the request control to clamp the strength, the adjustment 速比, can meet the actual needs.

Fifth, concluding remark

Has clamped the strength control valve through the experimental study the operational factor; In order to prevent the integrator wound around, designs had the PID controller which the forward feed anti- wound around, and using to clamps in the strength control system which designed; To steps up the strength control model which designs to carry on the simulation experiment, and to was loaded with should step up the strength controller the integrated control system to carry on has loaded a car the experiment.

The result indicated, designs the controller is reliable, has the practical value.