Abstract:
A method for synchronizing control of a road test simulator and a road test simulator having four rollers ( 10, 20, 30, 40 ) and four asynchronous motors ( 12, 22, 32, 42 ). Each of the asynchronous motors is used to actuate one of the rollers. Each roller is associated with a speed/angle rotation. The synchronization control takes place electronically and in the manner of a ring structure.

Description:
[0001]    This is a Continuation of International Application PCT/DE02/00026, with an international filing date of Jan. 8, 2002, which was published under PCT Article 21(2) in German, and the disclosure of which is incorporated into this application by reference. 
     
    
     
       FIELD OF AND BACKGROUND OF THE INVENTION  
         [0002]    The invention relates to a road test simulator and to a method for synchronizing control of a road test simulator.  
           [0003]    In order to inspect a vehicle after its final assembly, various tests are ordinarily conducted. These tests are often carried out as actual road tests, which renders the testing costly.  
           [0004]    So as to abbreviate or to completely replace such costly road tests, it is known in the art to provide a road test simulator, which can be used to simulate the irregularities of a road surface. Most prior-art simulators, however, have rollers with a non-adjustable profile. As a result they are inflexible and thus suitable only for limited testing of a vehicle.  
           [0005]    German reference DE 299 18 490.0 describes a road test simulator with profiled rollers. Each of these rollers is provided with a plurality of profile-imparting blocks along its outer circumference. These blocks can be adjusted in the radial direction of the roller to change the profile of the roller. Each roller ranges in width from a single to a double width of the vehicle tire. The road test simulator is additionally provided with a computer unit to implement a test program. With the aid of this test program, the computer unit can be programmed, for example, to simulate different road surfaces automatically by adjusting the blocks of the rollers.  
           [0006]    Also, U.S. Pat. No. 4,635,472 discloses an apparatus for testing a vehicle. Each vehicle of the vehicle to be tested has a corresponding own rotary drum. Every rotary drum is driven by a separate synchronous electric motor. The motors are coupled via a common frequency control unit to an electric power source. To ensure that the synchronous motors have the same rotational speed, changes in torque are detected by torque measurement devices respectively coupled to each motor. The measured values of the torque measurement devices are supplied to a central evaluation device, which derives an adjustment signal for the central frequency control unit.  
           [0007]    European Patent Application 0 567 781 discloses a method and an apparatus for controlling electric motors. Two or more motors with defined differences in rotational speed are to be driven. This is accomplished using sensors to generate pulse trains in response to increasing swing angles of the motors. The motors are then temporarily either partly or completely disconnected from the power supply on the basis of the differences in the pulse trains.  
           [0008]    In addition, it is conventional in the art to ensure that the rollers of a road test simulator are synchronized, through the use of a mechanical coupling of the rollers.  
         OBJECTS OF THE INVENTION  
         [0009]    One object of the invention is to provide a new method for the synchronization control of a road test simulator, e.g., in order to increase the flexibility thereof.  
         SUMMARY OF THE INVENTION  
         [0010]    According to one formulation of the invention, this object is attained by a road test simulator that includes four rollers and four asynchronous motors, wherein each of the asynchronous motors drives a respective one of the rollers, four control units, wherein each of the rollers is assigned to a respective one of the control units, and a synchronization control. The synchronization control is effected electronically in accordance with a ring structure such that a given one of the control units assigned to a given one of the rollers receives a synchronization pulse and an actual speed value for the given control unit and receives a further synchronization pulse and a further actual speed value for a further one of the control units assigned to a preceding one of the rollers.  
           [0011]    According to another formulation, the invention is directed to a method that includes assigning a master function to a first of four rollers of a road test simulator, defining a speed setpoint for control of the roller acting as the master, detecting an actual speed value of the roller acting as the master, defining the detected actual speed value of the roller acting as the master as a speed setpoint for controlling a second of the four rollers, detecting an actual speed value of the second roller, and controlling the speed of the second roller to match the actual speed value of the second roller to the speed setpoint.  
           [0012]    Advantageous embodiments and further developments of the invention are described herein below.  
           [0013]    One advantage stemming from the invention is, in particular, the ability to provide a specific torque for the driving gear of the vehicle during testing, to simulate, thereby, uphill or downhill driving. It is further possible to change the positioning of the profiled rollers in relation to each other, and thereby to change the sequence of the simulated road surfaces in vibration tests. By using suitable control releases, test routines can be implemented simply and quickly for front, rear and all wheel drive vehicles. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    Further advantageous features of the invention will now be described by way of example with reference to the figures in which:  
         [0015]    [0015]FIG. 1 is a block diagram illustrating the interaction of individual components of a road test simulator according to an embodiment of the invention,  
         [0016]    [0016]FIG. 2 is a detailed structure diagram of the control in one possible operating mode of a road test simulator embodying the invention, and  
         [0017]    [0017]FIG. 3 is a detailed structure diagram of the control in another possible operating mode of the road test simulator. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    A road test simulator according to the embodiment of the invention described here can be operated in two operating modes: operating mode  1 : “roller drives vehicle” and operating mode  2 : “vehicle drives roller.” 
         [0019]    In the operating mode  1 , “roller drives vehicle,” a rotational speed setpoint is defined by means of a higher-level control via, e.g., a control panel. This speed setpoint is used to control asynchronous motors, which in turn drive rollers on which the wheels of the vehicle are positioned. The road test simulator control ensures that all four rollers are operated in angular synchronization, taking into account, if circumstances warrant, a predefinable relative position of the rollers in relation to each other. In this operating mode, the brakes of the vehicle are not applied and the clutch is disengaged.  
         [0020]    In the operating mode  2 , “vehicle drives roller,” a driver of the vehicle indirectly defines the rotational setpoint speed by actuating the gas pedal of the vehicle. If the clutch of the vehicle is engaged, actuating the gas pedal causes the two wheels driving the vehicle to rotate and a corresponding force to be transmitted to the rollers. In this case, too, the road test simulator control ensures an angular synchronization of all the rollers, taking into account, if appropriate, a predefinable offset angle.  
         [0021]    [0021]FIG. 1 shows a block diagram illustrating the interaction of the individual components of a road test simulator according to the described embodiment of the invention.  
         [0022]    The road test simulator depicted has four rollers  10 ,  20 ,  30 ,  40 . During the testing operation, the left front wheel of the motor vehicle is positioned on the roller  20 . The roller  20  is connected with an asynchronous motor  22  with interposed gearing  27 . This asynchronous motor is controlled by an inverter  26  with integrated speed/angle control  28 . The asynchronous motor  22  is equipped with a digital tachometer  25  that emits a plurality of pulses, e.g.  1024 , with each revolution of the motor. The output signal of the digital tachometer  25  is supplied to the speed control as an actual speed value. The roller  20  has a synchronization marker  23 . When this synchronization marker passes a sensor  24  during one rotation of the roller, this sensor supplies a synchronization pulse to the speed/angle control  28 . Thus, the speed/angle control knows the absolute position of the roller relative to the sensor  24 .  
         [0023]    In addition, the speed/angle control  28  also receives a synchronization pulse of the sensor  34  and the pulses generated by a digital tachometer  35 .  
         [0024]    During the testing operation, the right front wheel of the vehicle is positioned on the roller  10 . The roller  10  is connected with an asynchronous motor  12  with interposed gearing  17 . This asynchronous motor is controlled by an inverter  16  with integrated speed/angle control  18 . The asynchronous motor  12  is equipped with a digital tachometer  15  that emits a plurality of pulses, e.g.  1024 , with each revolution of the motor. The output signal of the digital tachometer  15  is supplied to the speed control as an actual speed value. The roller  10  has a synchronization marker  13 . When this synchronization marker passes a sensor  14  during one rotation of the roller, this sensor supplies a synchronization pulse to the speed/angle control  18 . Thus, the speed/angle control knows the absolute position of the roller relative to the sensor  14 . The speed/angle control  18  further receives the synchronization pulse of the sensor  24  and the pulses generated by the digital tachometer  25 .  
         [0025]    During the testing operation, the right rear wheel of the motor vehicle is positioned on the roller  40 . The roller  40  is connected with an asynchronous motor  42  with interposed gearing  47 . This asynchronous motor is controlled by an inverter  46  with integrated speed/angle control  48 . The asynchronous motor  42  is equipped with a digital tachometer  45  that emits a plurality of pulses, e.g.  1024 , with each revolution of the motor. The output signal of the digital tachometer  45  is supplied to the speed control as an actual speed value. The roller  40  has a synchronization marker  43 . When this synchronization marker passes a sensor  44  during one rotation of the roller, this sensor supplies a synchronization pulse to the speed/angle control  48 . The speed/angle control  48  further receives the synchronization pulse of the sensor  14  and the pulses generated by the digital tachometer  15 .  
         [0026]    During the testing operation, the left rear wheel of the motor vehicle is positioned on the roller  30 . The roller  30  is connected with an asynchronous motor  32  with interposed gearing  37 . This asynchronous motor is controlled by an inverter  36  with integrated speed/angle control  38 . The asynchronous motor  32  is equipped with a digital tachometer  35  that emits a plurality of pulses, e.g.  1024 , with each revolution of the motor. The output signal of the digital tachometer  35  is supplied to the speed control as an actual speed value. The roller  30  has a synchronization marker  33 . When this synchronization marker passes a sensor  34  during one rotation of the roller, this sensor supplies a synchronization pulse to the speed/angle control  38 . The speed/angle control  38  further receives the synchronization pulse of the sensor  44  and the pulses generated by the digital tachometer  45 .  
         [0027]    The road test simulator depicted in FIG. 1 makes it possible to test front, rear and all wheel drive vehicles. During operation of the simulator, one of the rollers is assigned a master function while the other rollers are slaves. For vehicles with front wheel drive, for example, the left front roller  20  is assigned a master function. For vehicles with rear-wheel drive, for example, the right rear roller  40  is assigned a master function. For vehicles with all wheel drive, for example, the left front roller  20  or the left rear roller  30  can be assigned a master function.  
         [0028]    If the depicted road test simulator is to be used in the operating mode  1 , “roller drives vehicle,” to test vehicles with front wheel drive, the left front roller  20  is assigned a master function—as described above. In this operating mode, a higher-level control  50  predefines a rotational speed set point for the speed/angle control  28 . The speed/angle control  28  controls the inverter  26  as a function of the speed set point in such a way that the inverter suitably controls the asynchronous motor  22  as a function of the speed setpoint and the respectively required motor torque. The asynchronous motor, in turn, drives the roller  20  via the gearing  27 , so that the roller rotates at a speed that is a function of the speed setpoint.  
         [0029]    In this operating mode, in which the roller  20  is assigned a master function, the ring structure of the control shown in FIG. 1 is interrupted at the point indicated by the dashed line Ti because control with respect to the master is limited to the setpoint speed predefined by the higher-level control  50 . Fine-tuning or angular control as a function of the pulses derived from the digital tachometer  35  and the sensor  34  is omitted.  
         [0030]    In contrast, if the road test simulator depicted is to be used to test vehicles with rear wheel drive, the right rear roller  40  is assigned a master function—as described above. In this operating mode, a speed set point is predefined for the speed/angle control  48  by the higher-level control  50 . The speed/angle control  48  controls the inverter  46  as a function of the speed setpoint in such a way that the inverter controls the asynchronous motor  42  as a function of the speed setpoint. The asynchronous motor, in turn, drives the roller  40  via the gearing  47 , so that the roller rotates at a speed that is a function of the speed setpoint.  
         [0031]    In this operating mode, in which the roller  40  is assigned a master function, the ring structure of the control shown in FIG. 1 is interrupted at the point indicated by the dashed line T 2  because control with respect to the master is limited to the setpoint speed predefined by the higher-level control  50 . Fine-tuning or angular control as a function of the pulses derived from the digital tachometer  15  and the sensor  14  is omitted.  
         [0032]    [0032]FIG. 2 is a detailed structure diagram of the control in an operating mode in which vehicles with front wheel drive are tested. The vehicle to be tested is positioned on the rollers  10 ,  20 ,  30 ,  40  without brakes applied and with clutch disengaged, i.e. in the operating mode  1 , “roller drives vehicle.” In this operating mode, the front left roller  20  is assigned a master function. The other rollers  10 ,  30  and  40  are matched to the roller  20  utilizing an electronic synchronization control. In the embodiment shown, the front right wheel is positioned on the roller  10 , the front left wheel is positioned on the roller  20 , the hind left wheel is positioned on the roller  30 , and the hind right wheel is positioned on the roller  40 .  
         [0033]    [0033]FIG. 2 shows that each roller  10 ,  20 ,  30 ,  40  is assigned its own control loop with asynchronous motor  12 ,  22 ,  32 ,  42  driving the corresponding roller via gearing  17 ,  27 ,  37 ,  47 .  
         [0034]    The control loop assigned to the roller  20  has a ramp function generator  28   a , an actual speed/position detector  28   b , an adder  28   c , a displacement/angle controller  28   d  and a limiter  28   e . The control loop associated with the roller  20  further has a ramp function generator  26   a , an adder  26   b , a rotational speed controller  26   c , a limiter  26   d , a current controller  26   e  and a firing unit  26   f.    
         [0035]    The control loop assigned to the roller  10  has a ramp function generator  18   a , an actual speed/position detector  18   b , an adder  18   c , a displacement/angle controller  18   d  and a limiter  18   e . The ramp function generator associated with the roller  10  further has a ramp function generator  16   a , an adder  16   b , a rotational speed controller  16   c , a limiter  16   d , a current controller  16   e  and a firing unit  16   f.    
         [0036]    The control loop assigned to the roller  40  has a ramp function generator  48   a , an actual speed/position detector  48   b , an adder  48   c , a displacement/angle controller  48   d  and a limiter  48   e . The ramp function generator associated with the roller  40  further has a ramp function generator  46   a , an adder  46   b , a rotational speed controller  46   c , a limiter  46   d , a current controller  46   e  and a firing unit  46   f.    
         [0037]    The control loop assigned to the roller  30  has a ramp function generator  38   a , an actual speed/position detector  38   b , an adder  38   c , a displacement/angle controller  38   d  and a limiter  38   e . The ramp function generator associated with the roller  30  further has a ramp function generator  36   a , an adder  36   b , a rotational speed controller  36   c , a limiter  36   d , a current controller  36   e  and a firing unit  36   f.    
         [0038]    The elements  28   a ,  28   b ,  28   c ,  28   d  and  28   e  of the control loop assigned to the roller  20  are shown as a dashed line in FIG. 2 because they are disabled in the current operating mode, as is indicated by the dashed line T 1  in FIG. 1.  
         [0039]    A rotational speed setpoint is supplied to the input of the ramp function generator  26   a  by way of a higher-level control, e.g. via a control panel. The purpose of the ramp function generator is to ensure that the speed setpoint of the downstream circuit is supplied in accordance with a ramp. This has the effect that the full speed setpoint is present only after a preset time interval has elapsed.  
         [0040]    The output signal of the ramp function generator  26   a  is supplied to the adder  26   b , which receives the actual speed value with negative sign from the asynchronous motor  22  derived from the tacho pulses of the digital tachometer  25 . The output signal of the adder  26   b  reaches the speed controller  26   c . The speed controller&#39;s output signal is fed via the limiter  26   d  to the current controller  26   e , whose output in turn is connected with the firing unit  26   f . The firing unit converts the signal into electrical pulses, which are used to suitably control the semiconductor valves of the inverter  26 . The asynchronous motor  22  drives the front left roller  20  via the gearing  27 . The motor voltage or motor current arising in the asynchronous motor then corresponds to the desired motor speed and the desired motor torque.  
         [0041]    The actual speed value of the master derived from the asynchronous motor  22  is supplied as a rough speed setpoint via the higher-level control  50  to the input of the ramp function generator  16   a  of the control loop associated with the roller  10 . Through the ramp function generator  16   a , this actual speed value reaches the adder  16   b . The adder further receives a speed correction value and, with a negative sign, the actual speed value derived from the digital tachometer  15 .  
         [0042]    The speed correction value supplied to the adder  16   b  is determined using an offset setpoint of the pulses derived from the digital tachometer  25  of the master, the digital tachometer  15 , the sensor  24  of the master and the sensor  14  of the roller  10 . The offset setpoint is predefined by the higher-level control  50  and supplied to the adder  18   c  via the ramp function generator  18   a . The pulses derived from the digital tachometers  25  and  15  and from the sensors  24  and  14  are used to determine a position deviation signal in the speed/position detector  18   b . This signal is supplied to the adder  18   c  with a negative sign.  
         [0043]    The output signal of the adder  18   c  is supplied to the displacement/angle controller  18   d . The output signal of the displacement/angle controller reaches the adder  16   b  via the limiter  18   e  and influences the downstream speed control in the manner of a fine correction.  
         [0044]    The output signal of the adder  16   b  reaches the speed controller  16   c . The output signal of the speed controller is supplied to the current controller  16   e  via the limiter  16   d . In the firing unit downstream of the current controller, the signal is converted into electrical pulses, which are used to control the asynchronous motor  12  via semiconductor valves (IGBTs). The asynchronous motor  12  drives the front right roller  10  via the gearing  17 .  
         [0045]    The actual speed value of the master derived from the asynchronous motor  22  is supplied as a rough speed setpoint via the higher-level control  50  to the input of the ramp function generator  46   a  of the control loop assigned to the roller  40 . Through the ramp function generator  46   a , this actual speed value reaches the adder  46   b . The adder further receives a speed correction value and, with a negative sign, the actual speed value derived from the pulse generator  45 .  
         [0046]    The speed correction value supplied to the adder  46   b  is determined using an offset setpoint of the pulses derived from the digital tachometer  15  of the asynchronous motor  12 , the digital tachometer  45 , the sensor  14  of the roller  10  and the sensor  44  of the roller  40 . The offset setpoint is predefined by the higher-level control  50  and supplied to the adder  48   c  via the ramp function generator  48   a . The pulses derived from the digital tachometers  15  and  45  and from the sensors  14  and  44  are used to determine a position deviation signal in the actual speed/position value detector  48   b . This signal is supplied to the adder  48   c  with a negative sign.  
         [0047]    The output signal of the adder  48   c  is supplied to the displacement/angle controller  48   d . The output signal of the displacement/angle controller reaches the adder  46   b  via the limiter  48   e  and influences the downstream speed control in terms of a fine correction.  
         [0048]    The output signal of the adder  46   b  reaches the speed controller  46   c . The output signal of the speed controller is supplied to the current controller  46   e  via the limiter  46   d . In the firing unit downstream of the current controller, the signal is converted into electrical pulses, which are used to control the asynchronous motor  42  via semiconductor valves (IGBTs). The asynchronous motor  42  drives the rear right roller  40  via the gearing  47 .  
         [0049]    The actual speed value of the motor derived from the asynchronous motor  22  is supplied as a rough speed setpoint via the higher-level control  50  also to the input of the ramp function generator  36   a  of the control loop assigned to the roller  30 . Through the ramp function generator  36   a , this actual speed value reaches the adder  36   b . The adder further receives a speed correction value and, with a negative sign, the actual speed value derived from the pulse generator  35 .  
         [0050]    The speed correction value supplied to the adder  36   b  is determined using an offset setpoint of the pulses derived from the digital tachometer  45  of the asynchronous motor  42 , the digital tachometer  35 , the sensor  44  of the roller  40  and the sensor  34  of the roller  30 . The offset setpoint is predefined by the higher-level control  50  and supplied to the adder  38   c  via the ramp function generator  38   a . The pulses derived from the digital tachometers  45  and  35  and from the sensors  44  and  34  are used to determine a position deviation signal in the actual speed/position value detector  38   b , which is supplied to the adder  38   c  with a negative sign.  
         [0051]    The output signal of the adder  38   c  is supplied to the displacement/angle controller  38   d . The output signal of the displacement/angle controller reaches the adder  36   b  via the limiter  38   e  and influences the downstream speed control as a fine correction.  
         [0052]    The output signal of the adder  36   b  reaches the speed controller  36   c . The output signal of the speed controller is supplied to the current controller  36   e  via the limiter  36   d . In the firing unit downstream of the current controller, the signal is converted into electrical pulses, which are used to control the asynchronous motor  32  via semiconductor valves (IGBTs). T he a synchronous motor  32  drives the rear left roller  30  via the gearing  37 .  
         [0053]    Using the control structure shown in FIG. 2, the slave rollers  10 ,  30  and  40  are operated in angular synchronization relative to the roller  20 , which acts as the master. A speed setpoint is predefined for the control loop of the roller  20  by a higher-level control. The actual speed value of the asynchronous motor  22  assigned to the roller  20  is detected and supplied as a rough speed setpoint to the speed/angle controllers associated with the rollers  10 ,  30  and  40  via the higher-level control  50 .  
         [0054]    In the embodiment shown, the ring structure of the control is interrupted by disabling the displacement/angle controller  28   d , which in FIG. 2 is indicated by the dashed lines. This disabling can be effected, for example, by inhibiting the angle controller.  
         [0055]    Using the limiters  16   d ,  26   d ,  36   d  and  46   d  the output signal of the respective speed controller  16   c ,  26   c ,  36   c  and  46   c  can be limited to prevent overload of the corresponding asynchronous motor  12 ,  22 ,  32 ,  42 .  
         [0056]    Using the limiters  18   e ,  38   e  and  48   e , the additional setpoint that is present at the output of the respective displacement/angle controller  18   d ,  38   d  and  48   d  can be limited to a predefined maximum value. This makes it possible to adjust the rate of the offset angle adjustment.  
         [0057]    [0057]FIG. 3 shows a detailed structure diagram of the control in operating mode  2 , “vehicle drives roller,” for a vehicle with front wheel drive. Accordingly, the front left roller  20  is assigned a master function in FIG. 3 as well. The other rollers  10 ,  30  and  40  are matched to the roller  20  using the electronic synchronization control.  
         [0058]    The structure diagram of FIG. 3 is distinguished from that shown in FIG. 2 in that, in FIG. 3, a rotational speed setpoint of zero is predefined for the speed control loop with the components  26   a ,  26   b ,  26   c ,  26   d ,  26   e  and  26   f  and no motor torque at all is permitted (torque limit equals zero). This is indicated by the dashed lines in FIG. 3.  
         [0059]    The setpoint speed in this operating mode is defined by the driver of the test vehicle through a corresponding actuation of the gas pedal. The corresponding actual speed of the roller  20 , or the motor  22  assigned thereto, is measured and supplied as the speed setpoint to the control loop associated with the roller  10 . The synchronization control is, in other respects, effected in the same manner as described above with reference to FIG. 2.  
         [0060]    The above-described control processes may require not only the angular synchronism (synchronism of all four wheels) but also synchronization (reproducibility oft he road surface) and an offset angle adjustment (change of the road surface). In such an event, the synchronization pulses or zero pulses derived from the respective sensor  14 ,  24 ,  34 ,  44  and identifying a specific positioning on the roller must also be analyzed. In this synchronization process, the synchronous pulses of the respective master and the respective slave must be brought into a certain position relative to one another. The angular offset between the two synchronization markers is characterized by the number of the incoming tacho pulses of the respective slave drive between the two synchronization markers.  
         [0061]    If vehicles with rear wheel drive are tested in the same operating mode  2 , the rear right roller  40  is assigned a master function. To implement this operating mode, the control loop is interrupted, in analogous manner, by an omitted angle controller release to  48   d . The speed setpoint zero is predefined for the speed controller  46   c . The torque limit  46   d  is set to zero.  
         [0062]    By predefining torque limits unequal to zero in operating mode  2 , “vehicle drives roller,” it is possible to specifically apply torques to the motor and, via the gearing, to the roller during the operation of the vehicle because the speed controller is overridden (speed setpoint equal to zero, actual speed value unequal to zero). These torques can simulate uphill or downhill driving depending on the torque direction.  
         [0063]    Thus, a road test simulator according to the invention can be operated in many different operating modes. A transition between the possible operating modes can be simply and quickly effected by an electronic definition of parameters.  
         [0064]    The above description of the preferred embodiments has been given by way of example. From the disclosure given, those skilled in the art will not only understand the present invention and its attendant advantages, but will also find apparent various changes and modifications to the structures and methods disclosed. It is sought, therefore, to cover all such changes and modifications as fall within the spirit and scope of the invention, as defined by the appended claims, and equivalents thereof.