Simulated engine characteristic control system

Abstract: The simulated engine characteristic control system for transmission transient performance tests for automotive vehicles comprises a motor (2) for driving an input shaft of the tested transmission (1). A pick-up (5) detects revolution of the motor. A simulating circuit (not shown) simulates either an opening angle (O) of the throttle of the engine to be associated with the tested transmission or the intake manifold pressure of the engine. An engine characteristic generator (4) generates a torque command signal (T*) according to predetermined engine revolution/torque characteristic curves, in response to the signals (N,ϑ) from the pick-up (5) and the simulating circuit. A torque/current transducer (11) transduces the torque command signal (T*) to an analog current command signal (I₁) according to a predetermined torque/current characteristic. Means (12,16) are provided for compensating the current command signal (I₁) in consideration of a torque component occurring at an axial moment of inertia of the rotating member of the motor (2) during acceleration or deceleration of the motor, and a field characteristic of a field coil of the motor, representing the output torque/revolution of the motor. The motor (2) is drivingly controlled in response to a current command signal (I*) compensated through the compensating means (12,16).

Description: The present invention relates to a simulated engine characteristic control system for power train performance tests for automotive vehicles, particularly to a system utilized for transient performance tests for automotive transmissions, for example an endurance test for synchronizing devices used in manual transmissions, wherein a test is made to simulate stress applied to the synchronizing devices when shifting during high acceleration or quick deceleration, and a feeling test for automatic transmissions, wherein a test is made to determine whether or not shifting is smoothly executed during simulated acceleration and/or deceleration, specifically to a system in which transient performance tests for transmissions can be simulated by replacing the internal combustion engine associated with a transmission to be tested with a direct-current (DC) motor serving as a driving device. Conventionally, there have been proposed and developed various transient performance test machines for automotive vehicles. In transmission performance tests, the engine associated with the transmission being tested is in general utilized as a driving device for the tested transmission. In this situation, many ancillary facilities are necessitated to operate the engine, thereby resulting in a relatively large test space. Furthermore, the horsepower generated from the engine may vary slightly due to changes in the ambient temperature during the performance test. For this reason, it was desirable that the engine drive method be replaced with a motor drive method. As is generally known, since an axial moment of inertia of the rotor employed in the motor is much greater than that of the rotating member of the engine, such as an engine crankshaft and a flywheel, such motor drive devices cannot sufficiently simulate changes in engine speed due to the low responsiveness of such devices when compared to an engine. Therefore, recently, there has been proposed and developed a transmission transient performance test machine including a relatively low inertia motor drive device which can generate output revolutions and output torques similar to an engine which operates in combination with a speed-increasing gear so as to have an axial moment of inertia similar to the rotating member of an engine. This low inertia of the rotor of the DC motor is accomplished by a highly rigid rotating shaft and a cooling device being capable of efficiently cooling the motor. One such conventional transmission transient performance test machine is shown in Fig. 1. Referring now to Fig. 1, the input shaft of a tested transmission 1 is connected through a torquemeter 8 to a low inertia DC motor 2 including a speed-increasing gear, while the output shaft of the transmission 1 is connected to a dynamometer 3 serving as a load applied to the transmission 1. Reference numeral 4 denotes an engine characteristic generator which generates a torque command signal T* in accordance with an engine revolution and torque characteristic map being comprised of a plurality of engine revolution and torque characteristic curves depending on the respective opening angle of the throttle valve of the engine. The map is assumed and preset in the engine characteristic generator 4, on the basis of the characteristics associated with the engine normally coupled with the tested transmission. The engine characteristic generator 4 is connected to a throttle opening angle signal generator (not shown) or an intake manifold pressure signal generator (not shown) and generates a torque command signal to a torque controller 7, in response to either a throttle opening angle signal ϑ from the above mentioned throttle opening angle signal generator or an intake manifold pressure signal from the above mentioned intake manifold pressure signal generator. The engine characteristic generator 4 also receives an actual revolution signal N through a pulse pick-up 5, disposed in the vicinity of the rotating shaft of the DC motor 2 for detecting actual revolution of the DC motor 2, and a frequency/voltage transducer 6, processing pulses from the pulse pick-up 5 to a voltage signal indicative of the actual rpm of the DC motor 2. For instance, when the engine characteristic generator 4 receives the signal ϑ i indicative of a throttle opening angle of 100 %, the generator 4 generates the torque command signal T* determined according to the actual revolution N of the DC motor 2, plotted on the uppermost curve shown in Fig. 1, indicating the engine revolution and torque relationship at a full throttle state. Conversely, when the engine characteristic generator 4 receives the signal ϑ o indicative of a throttle opening angle of 0 %, the generator 4 outputs the torque command signal T* determined according to the actual revolution N, plotted on the lowermost curve shown in Fig. 1, indicating the revolution and torque relationship at a fully closed throttle valve state. In the engine characteristic generator 4 as shown in Fig. 1, although the two engine revolution and torque curves are indicated between the uppermost and lowermost curves, more engine revolution and torque curves may be stored in the generator 4, depending on throttle opening angles of the engine. For instance, ten engine revolution and torque curves may be selected according to step-by-step throttle opening angles. The torque controller 7 compares the torque command signal T* from the engine characteristic generator 4 and the detected output torque signal T from the previously described torquemeter 8, and thereafter controls the DC motor 2 in such a manner as to reach the detected output torque T to the torque command signal T*. In other words, the input torque applied to the tested transmission 1 is adjusted by the feedback control on the basis of the torque output from the DC motor 2. In this manner, in conventional transmission transient performance test machines, the torquemeter detects the actual output torque T from the DC motor and thereafter the detected torque T is controlled in a manner so as to reach the command torque T* by feedback control, thereby permitting high accuracy of the output torque T. However, the responsiveness of conventional test machines is relatively low, for example 1 to 3 sec due to delay of the feedback control with regard to the output torque from the DC motor. Such conventional test machines may not satisfactorily respond to the previously described transmission transient performance tests. In order to improve the responsiveness of the torque control, there has been proposed and developed another type transmission transient performance test machine wherein output torque from a DC motor for driving a tested transmission is derived from an actual current or voltage applied to the DC motor. In this case, since the output torque from the DC motor is not determined by a torque signal from a torquemeter disposed in the output side of the DC motor but by a current or voltage applied to the input side of the DC motor, the responsiveness of the test machine is improved. However, when comparing the previously described two conventional transmission transient performance test machines, the latter is inferior to the former with regard to the accuracy of the output torque control of the DC motor. It is, therefore, in view of the above disadvantages, an object of the present invention to provide a simulated engine characteristic control system having high responsiveness and high accuracy, serving for power train transient performance tests, such as transmission transient performance tests, for automotive vehicles. The present invention provides a simulated internal combustion engine characteristic control system for testing performance of a power train for an automotive vehicle, comprising: an electric motor for driving an input shaft of a power train for an automotive vehicle; means for monitoring revolution of the electric motor the monitoring means generating a signal indicative of the revolution of the electric motor; means for simulating either an opening angle (ϑ) of a throttle valve of the internal combustion engine or the intake manifold pressure of the internal combustion engine, the simulating means generating a signal indicative of the throttle valve opening angle (ϑ) or the intake manifold pressure; and an engine characteristic generator for generating a torque command signal (T*) according to predetermined engine revolution and torque characteristic curves memorized therein, in response to the signals from both the monitoring means and the simulating means; characterised by: means for transducing the torque command signal (T*) to an electric current command signal according to a predetermined torque and current characteristic curve of the electric motor memorized therein; first compensating means for compensating the current command signal by a compensatory current signal corresponding to the torque component occurring during acceleration or deceleration of the electric motor, the compensation being based on the axial moment of inertia of the rotating member of the electric motor; and second compensating means for compensating a first compensated current command signal from the first compensating means according to a field characteristic of a field coil of the electric motor, the field characteristic representing the output torque and revolution speed of the electric motor; and control means for drivingly controlling the electric motor in response to a final compensated current command signal (I*) from the second compensating means. The control means preferably executes feedback control for controlling an electric current input to the motor in response to the final compensated current command signal compensated through the compensating means. Preferably, the motor may comprise a direct current motor. The motor may be combined with a speed-increasing gear. The monitoring means includes a pulse pick-up disposed in the vicinity of the rotating shaft of the motor. The torque and current characteristic curve memorized in the transducing means is predetermined by the input current applied from the controlling means to the motor and an actual output torque generated from the motor when applying its input current to the motor. The actual output torque is detected by a torquemeter connected to the output shaft of the motor. The first compensating means may include means for generating an angular acceleration signal on the basis of the revolution signal from the monitoring means, means for generating a signal indicative of the axial moment of inertia of the rotating member, means for calculating the torque component on the basis of the angular acceleration signal and the axial moment of inertia signal, the calculating means generating the compensatory current signal corresponding to the torque component, and an adder-subtracter for adding the compensatory current signal to the current command signal or subtracting the compensatory current signal from the current command signal, during acceleration or deceleration of the motor. The second compensating means may include means for generating a compensatory coefficient signal according to the field characteristic, in response to the revolution signal, and a divider for dividing the current command signal compensated through the first compensating means by the cmpensatory coefficient signal. THE DRAWINGS Fig. 1 is a system diagram illustrating the main components of a conventional transmission transient performance test machine. Fig. 2 is a system diagram illustrating the main components of a transmission transient performance test machine including a simulated engine characteristic control system according to the invention. THE PREFERRED EMBODIMENT The principles of the present invention, applied to a simulated engine characteristic control system for power train transient performance tests for automotive vehicles, are illustrated in Fig. 2. In the preferred embodiment, the same reference numerals used to designate elements in the conventional transmission transient performance test machine as shown in Fig. 1 will be applied to corresponding elements used in the embodiment according to the invention for the purpose of comparing the conventional system and the improved system. Referring now to Fig. 2, the engine characteristic generator 4 outputs a torque command signal T* to a torque and current transducer 11, in response to the throttle opening angle signal ϑ as previously described in the prior art disclosure, and then the torque command signal is processed into an electric current command signal I₁ in accordance with a torque and current characteristic curve of the DC motor 2. Note that the torque and current characteristic curve is predetermined by two parameters, namely a current I applied to the input side of the DC motor and an output torque T from the DC motor 2, detected by the torquemeter 8 disposed between the DC motor 2 and the input shaft of the tested transmission 1 finally connected to the dynamometer 3. Since the above mentioned torque and current characteristics of the DC motor gradually vary depending on various factors, such as changes in ambient temperature or deterioration of the field coil of the DC motor, preferably the torque and current relationship is calibrated just before the transmission transient performance tests are executed, so as to permit high accuracy of the output torque control of the DC motor. After calibration, the data is stored in the transducer 11 as a renewed torque and current characteristic curve. During testing, the torque command signal T* may be quickly converted into the current command signal I₁ according to the torque and current characteristic curve stored in the transducer 11. Furthermore, the current command signal I₁ is compensated through two compensation processes and thereafter the compensated current command signal I* is output into an electric current controller 18. One current compensation process is an adding/subtracting process executed by an adder-subtracter 12, wherein, during simulated acceleration or deceleration, a compensatory current signal corresponding to a torque component required to accelerate or decelerate the rotating member of the DC motor due to an axial moment of inertia thereof is added to the command signal I₁ or subtracted from the command signal I₁. As clearly seen in Fig. 2, the compensatory current signal is generated according to the following order. First, the pulse pick-up 5 which is disposed in the vicinity of the rotating shaft of the DC motor 2, outputs a pulse signal representative of the output revolution of the DC motor 2 to the frequency/voltage transducer 6. The transducer 6 processes the pulse signals into an analog signal N representative of the actual output revolution of the DC motor 2. The revolution signal N from the transducer 6 is output into the engine characteristic generator 4 and is also output into a differentiator 13. The differentiator 13 processes an angular speed derived from the revolution signal N into an angular acceleration signal dN/dt representative of an angular acceleration of the rotating member of the DC motor. Thereafter, the angular acceleration signal dN/dt is output from the differentiator 13 to an arithmetic logical unit 14. The unit 14 multiplies the angular acceleration signal dN/dt by an axial moment of inertia of the rotating member of the DC motor 2, derived from an inertia setting circuit 15 and thus calculate the torque component required to accelerate or decelerate the rotating member. Finally, the unit 14 converts the calculated torque component into the compensatory current value and outputs the compensatory current signal to the adder-subtracter 12. The current command signal I₁ compensated by the adder-subtracter 12 is output into a divider 16 as a compensated current command signal I₂. The other current compensation process is a dividing process executed by the divider 16, wherein the compensated current command signal I₂ is divided by a coefficient K depending on a field characteristic of the field coil of the DC motor 2. As seen in Fig. 2, the coefficient K is determined by a field characteristic curve stored in a field characteristic generator 17. The field characteristic generator 17 receives the revolution signal N from the transducer 6 and thereafter outputs a signal indicative of the coefficient K to the divider 16 in accordance with the field characteristic curve exhibiting the output torque and revolution relationship of the DC motor such that, when the output revolution N is less than a base speed N B , the output torque T is substantially constant, while as the output revolution N exceeds the base speed N B , the output torque T is exponentially lowered according to increase in the revolution N. As set forth, after final compensation of the current signal I₂ at the divider 16, the divider 16 outputs a final current command signal I* into an electric controller 18. The electric controller 18 detects the output current I of the DC motor 2 and operates the DC motor 2 in such a manner as to reach the output current I by feedback control. As will be appreciated from the above, the torque control of the tested transmission 1 is accomplished by current control of the DC motor 2 as previously described. Therefore, the engine characteristic simulation control system according to the invention, can provide a high responsiveness of torque control from the DC motor, substantially 0.02 to 0.03 sec. This is experimentally assured by the inventors of the invention. Moreover, since the torque and current characteristic data, stored in the transducer 11 generating the initial current command signal I₁, is easily, reliably calibrated and renewed, and thereafter the initial current command signal I₁ is compensated through the previously described two current compensation processes, such current control permits high accuracy torque control of the DC motor 2 in spite of the current control. Although in the preferred embodiment, the DC motor is used for the simulated engine characteristic control system, another type of motor may be used therefor.

Claims: A simulated internal combustion engine characteristic control system for testing performance of a power train for an automotive vehicle, comprising: an electric motor (2) for driving an input shaft of a power train (1) for an automotive vehicle; means (5,6) for monitoring revolution of the electric motor (2), the monitoring means generating a signal (N) indicative of the revolution of the electric motor; means for simulating either an opening angle (ϑ) of a throttle valve of the internal combustion engine or the intake manifold pressure of the internal combustion engine, the simulating means generating a signal indicative of the throttle valve opening angle (ϑ) or the intake manifold pressure; and an engine characteristic generator (4) for generating a torque command signal (T*) according to predetermined engine revolution and torque characteristic curves memorized therein, in response to the signals from both the monitoring means (5,6) and the simulating means; characterised by: means (11) for transducing the torque command signal (T*) to an electric current command signal according to a predetermined torque and current characteristic curve of the electric motor (2) memorized therein; first compensating means (12) for compensating the current command signal by a compensatory current signal corresponding to the torque component occurring during acceleration or deceleration of the electric motor (2), the compensation being based on the axial moment of inertia of the rotating member of the electric motor (2); and second compensating means (16) for compensating a first compensated current command signal from the first compensating means according to a field characteristic of a field coil of the electric motor (2), the field characteristic representing the output torque and revolution speed of the electric motor (2); and control means (18) for drivingly controlling the electric motor (2) in response to a final compensated current command signal (I*) from the second compensating means (16). A simulation control system as claimed in claim 1, wherein the said control means (18) executes feedback control for controlling an electric current input to the electric motor (2) in response to the final compensated current command signal (I*). A simulation control system as claimed in claim 2, wherein the torque and current characteristic curve memorized in the transducing means (11) is predetermined by the input current applied from the control means (18) to the electric motor (2) and an actual output torque (T) detected by a torquemeter (8) connected to the rotating member of the electric motor (2). A simulation control system as claimed in any preceding claim, wherein the electric motor (2) comprises a direct current motor. A simulation control system as claimed in any preceding claim, wherein the electric motor (2) is combined with a speed-increasing gear. A simulation control system as claimed in any preceding claim, wherein the monitoring means includes a pulse pick-up (5) disposed in the vicinity of the rotating member of the motor (2). A simulation control system as claimed in any preceding claim, wherein the first compensating means includes means (13) for generating an angular acceleration signal on the basis of the revolution signal (N) from the monitoring means (5,6), means (15) for generating a signal indicative of the said axial moment of inertia of the rotating member of the electric motor (2), means (14) for calculating the said torque component on the basis of the angular acceleration signal value and the axial moment of inertia signal value, the calculating means (14) generating the compensatory current signal corresponding to the said torque component, and an adder-subtracter (12) for adding the compensatory current signal to the current command signal during acceleration of the electric motor (2) and for subtracting the compensatory current signal from the current command signal during deceleration of the electric motor (2). A simulation control system as claimed in any preceding claim, wherein the second compensating means includes means (17) for generating a compensatory coefficient signal (K) according to the said field characteristic, in response to the revolution signal (N), and a divider (16) for dividing the said first compensated current command signal by the compensatory coefficient signal (K).

Inventors: GOTO TAKASHI, MARUKI TOSHIMITSU, MIZUSHINA FUMIO, GOTO, TAKASHI, MARUKI, TOSHIMITSU, MIZUSHINA, FUMIO
Applicants: MEIDENSHA ELECTRIC MFG CO LTD, KABUSHIKI KAISHA MEIDENSHA
Application year: 1989
Main classification: F02D41
IPC codes: G01M17, G01M13