DE19604220A1 - Control and limitation of vehicle speed - Google Patents

Abstract

A procedure for controlling and limiting the speed of a car has the speed influenced by an actuator that is adjusted by a controller to which a setpoint value varying with time is passed. The controller aims to keep the car speed close to this setpoint value. The increase of the setpoint value is changed according to the actual speed and the preset target speed. To change the setpoint speed, a time ramp is provided whose increase depends on the difference between the target and final speeds and upon the final speed itself. The change of the setpoint value is carried out using a delaying component of a filter function.

Description

State of the art

The invention relates to a method and a device to control or limit the driving speed of a Vehicle according to the generic terms of the independent Claims.

Such a method or device is known from DE-A 35 10 174 (U.S. Patent 4,747,051). There a vehicle speed controller is shown, in which in steady state to comply with given speed a speed controller is active, in dynamic operating states when approaching at the specified speed Accelerator. The accelerator works on the basis of the derived from the driving speed Acceleration of the vehicle. This signal must be strong be filtered so that the actual acceleration curve is smooth is. This in turn leads to a big delay in the Regulation and therefore not in all cases satisfactory transient response to the given Speed. Furthermore, to be a satisfactory  To make the transition from one controller to the other, the integral parts of the controller when changing to certain Values set. You must activate and Initialization of the accepting controller is complex Algorithms are used that also influence the Have transient response.

It is therefore an object of the invention to regulate or Limiting the driving speed of a motor vehicle with satisfactory settling to the given Specify speed in all operating situations.

This is due to the distinctive features of the independent claims achieved.

DE-A 28 42 023 is a vehicle speed controller known, in which to approach the actual speed the setpoint is a time-variable setpoint is specified. This setpoint is shown with a Ramp on predetermined slope, which if necessary depending on the difference between target and Actual speed assumes fixed values, depending on the difference between the driver's and the time-varying target speed or depending on the difference between the time variable setpoint and the actual value. These measures however, do not lead to a satisfactory result in all cases Settling behavior without complex algorithms must be used.

Advantages of the invention

The solution according to the invention causes a settling of the Speed of a vehicle to a target speed without complex initialization, activation algorithms  and without determining the acceleration of the vehicle reached.

It is particularly advantageous that this advantage in all Operating situations, even on steep mountains.

Application within the framework of a Speed limit to introduce the Speed to the target speed, including a stationary imprecise controller can be used.

It is particularly advantageous that the solution according to the invention is clear and easy to apply. Furthermore, no more adaption needed because the start conditions of the Regulations are simple on / off conditions. It is particularly advantageous that the controller precontrol, the Controller itself and the setpoint ramps separate from each other can be applied.

A complex calculation of the actual acceleration is not required because only one is required to activate the controller Threshold is queried.

Interference from the driver, especially just below the Target speed leading to a switch off and on again of the speed limiter lead through the Solution according to the invention largely eliminated.

Further advantages result from the following Description of exemplary embodiments or from the dependent claims.  

drawing

The invention is based on the in the drawing illustrated embodiments explained in more detail. It shows

Fig. 1 is an overview block diagram of a first embodiment of the solution according to the invention, which is further illustrated by the timing diagrams in Fig. 2. In FIGS. 3 and 4, the corresponding diagrams for a second embodiment are shown. Finally, FIG. 5 shows a flow chart which outlines a realization as a computer program for both embodiments.

Description of exemplary embodiments

Fig. 1 is an overview block diagram showing a first embodiment of the inventive solution. A control element that can be actuated by the driver for specifying the target or limiting speed is shown, which is connected to a storage element 14 via a line 12 . A line 16 leads from the storage element 14 to a connection point 18 to form the deviation between target and actual speed. A line 20 is fed to this comparison point 18 from a line 22 , which line emanates from a measuring device 24 for detecting the vehicle speed. An output line 26 of the comparison element 18 leads to a calculation element 28 , in which a time-variable target speed VSoll * is calculated depending on the difference between the target and actual speed. A line 17 also leads from line 16 to element 28 . Another input line is line 29 , which for activating and deactivating element 28 starts from line 48 described below. An output line 30 of the element 28 leads to a comparison point 32 , the output line 34 of which leads to the controller 36 . This controller represents a controller for the dynamic operating state (approaching the target speed). It is therefore also called acceleration controller. Its output line 38 leads via a switching element 40 to a connection point 42 , the output line 44 of which leads to a further connection point 46 . The switching element 40 is switched by a release element 50 via a line 48 . A line 52 is supplied to the linking point 42 from a characteristic diagram element 54 , to which a line 56 from the line 16 and a line 58 are supplied, via which the currently selected drive stage (actual gear) of the transmission of the vehicle is transmitted. According to the point of attachment 46 is supplied a line 60 which leads from a characteristic field element 62 to the linkage site 46th A line 66 , which starts from a line 68 described below, and a line 70 from line 58 are fed to the map element 62 . The output line 72 of the junction 46 leads via a switching element 74 to a selection stage 76 , the output line 78 of which leads to an actuating element 80 , preferably a throttle valve, which influences the vehicle speed. In addition to the line 72, the switching element 74 is supplied with a line 82 from a regulator 84 , to which a line 86 is supplied from the line 26 . This controller regulates the speed in the steady operating state and is therefore also called the speed controller. The switching element 74 is actuated via a line 88 , which also branches off from the line 26 . A line 90 , which is the output line of a map element 92 , is also fed to the selection element 76 . A line 94 is fed to this from a measuring device 96 for detecting the position of an accelerator pedal which can be actuated by the driver. Furthermore, a characteristic element 98 is provided, to which a line 100 , starting from the line 26 , is fed. In the characteristic element 98, a target acceleration is determined depending on the difference between target and actual speed, which is passed through line 68 to a junction 102nd The output line 104 leads to the release element 50 . A line 106 is fed to the comparison point 102 from a differentiation stage 108 in order to form the actual acceleration of the vehicle. A line 110 is fed from line 22 to this differentiation stage 108 . In addition to the line 104 , the release element 50 is also supplied with a line 112 from the line 90 , a line 114 from the line 52 and a line 116 from the line 60 .

The exemplary embodiment shown in FIG. 1 represents a speed limiter of a motor vehicle in which the controller 36 is active in the sense of an acceleration control in order to bring the speed up to the limiting speed, and the controller 84 is active in the sense of a speed control when the target speed is reached. Depending on the difference between target and actual speed, the two controllers are switched (by means of switching element 74 ). In the preferred exemplary embodiment, the controller 36 itself is activated when the speed drops below a predetermined value, which is substantially greater than the speed difference used to switch from the controller 36 to the controller 84 . To improve the control properties, the pre-controls of the controller 36 represented by the characteristic maps 54 and 62 are also provided. A first pilot control value VW1 is formed as a function of the drive level and the target speed in the map 54 . A second pilot control value VW2 is determined in the map 62 as a function of the target acceleration and the selected gear. The pilot controls are matched to the level road and unladen vehicle. This means that in the ideal case the pilot controls are sufficient to accelerate the vehicle, so that the controller 36 only has to correct deviations from this ideal setting. The pilot control values VW1 and VW2 are connected to the output line of the controller in the connection points 42 and 46 , preferably added together. Furthermore, they are fed to the release element 50 , which defines the starting conditions of the controller 36 and the setpoint ramps in the element 28 . The controller 36 and its pilot controls or the speed controller 84 generate setpoints for setting the control element 80 which influences the speed. The respective setpoint is fed to a selection stage 76 , which forms the smallest value of the respective controller setpoint and a setpoint derived via line 90 from the accelerator pedal actuation and passes it on to the actuating element 80 . The driver's setpoint is dependent on the degree of actuation of the accelerator pedal and possibly other operating variables, such as. B. the engine speed, determined in the map 92 .

In the preferred embodiment, a simple proportional controller is used as the controller 36 . The gain factor of the proportional controller depends on the selected gear.

The controller 36 is supplied with speed setpoints which are variable over time, so-called speed ramps, the incline of which depends on the target speed and the speed difference. As a result, the controller applies an additional manipulated variable to the pilot control (positive or negative). The time-changing setpoint speed is formed in the calculation element 28 , where the slope of the setpoint ramps is stored above the target speed and speed difference.

The ramps stored in the map 28 always run until the speed difference is reduced in such a way that it is possible to switch to the speed controller. In terms of control technology, this means that a variable I component is obtained for the proportional component of the controller 36 . The ramp slopes become flatter with increasing approach to the target speed. This means that the ramp runs longer on a steep mountain because the pilot control is geared towards the level and an unloaded vehicle.

The setpoint ramps and the setting signal of the controller 36 are determined in the preferred exemplary embodiment only under certain conditions, which are checked by the release element 50 . This releases the controller and the ramps when the driver comes with his specification via the pilot control, ie when he wants to set a speed that is above the target speed. For this reason, both the driver specification and the pilot control values are fed to the release element 50 . If the driver specification SollF is greater than the sum of the pre-control values VW1 and VW2, the switching element 40 is closed and the element 28 is activated. Depending on its input signals, the controller corrects the pilot control values so that the control element is set on the basis of the target value SollR formed from the controller and pilot control value, as long as it is smaller than the driver specification SollF. The setpoint ramps start from the actual speed at the time of activation, so that the control deviation of the controller is zero at the time of start. Therefore no initialization routines are necessary.

If the driver releases the accelerator pedal, ie if the driver specification falls below the pilot control, ie if the setpoint of the controller and the pilot control SollR again exceeds that of the driver SollF and the actuating element 80 is set depending on the driver setpoint, the ramp is stopped. If the driver setpoint then exceeds the controller setpoint again, the ramp is started again from the stopped value. The controller's setting variable is set to the value before switching off. If the driver z. B. a setpoint of 50% (the maximum throttle valve opening), the pilot control 35% (steep mountain), then the controller opens up to 15%. Then the ramp is stopped. If the driver then continues to pedal, e.g. B. to 70%, the controller ramp starts from the value 50% to a maximum of 70%. If the driver had not decreased to 70% but to 40%, the ramp and the controller would have been started from this 40%. However, if the driver specification drops below the pilot control, the ramp and the controller are started again from zero if the switch-on condition is present. The line necessary to carry out these functions for feeding the actual speed to element 28 and for setting the controller start values are not shown in FIG. 1 for reasons of clarity.

Another switch-on criterion for the controller and the ramp is the acceleration. You will be started when the Actual acceleration of the vehicle is greater than that dependent given by the speed difference Target acceleration. This measure prevents that when driving downhill if the driver specification is always below the Feedforward control (controller is not active because feedforward control greater than driver specification), the driving speed over the Target speed is led out. Hence the Controller (and the setpoint ramp) when the  Target acceleration started to overshoot the To prevent speed.

An example of the effect of the solution according to the invention is shown in FIGS. 2a-2c. Here, Fig. 2a shows the time course of the default values by the driver SollF and by the controller (plus feedforward control) SollR, Fig. 2b shows the time course of target acceleration ASoll and the actual acceleration AIf and Fig. 2c shows the time course of the actual speed VAct and the target or target speeds VSoll or VSoll *. It is assumed that the vehicle speed limiter is active, that is to say that the difference between the limit speed VSet specified by the driver and the actual speed is smaller than the activation threshold of the limiter. First, the vehicle accelerates on the basis of the setpoint SollF specified by the driver, which is smaller than that calculated by the controller precontrol. At a time T0, one of the activation criteria of the controller 36 is met. At time T0, the actual acceleration AIst exceeds the target acceleration. This means that from time T0, the target speed VSoll *, which changes in the form of a ramp, is predetermined for controller 36 . This then corrects the pilot values and thus SollR according to the difference between the target speed VSoll * and the actual speed. At time T0 ', the controller default value SollR calculated from the pilot control and controller value falls below the value SollF predetermined by the driver, so that the control element is set depending on the controller default value SollR. Due to the controller intervention, the actual acceleration of the vehicle decreases until time T1. At this point in time, the actual speed is in a range around the target speed, which leads to the activation of the speed controller that maintains the target speed. At time T1, controller 36 and the ramp are stopped. The preset value SollR is again provided by the feedforward control, but this no longer intervenes after the time T1, since this is set depending on the speed controller (or the driver preset value). The illustration according to FIG. 2 makes it clear that the solution according to the invention achieves a satisfactory settling of the actual speed to the target speed without great effort.

In Fig. 3, a second embodiment of the solution according to the invention. This differs in the points shown below from the exemplary embodiment according to FIG. 1. The elements which are used in the same way in both exemplary embodiments are not described in more detail. According to the second exemplary embodiment according to FIG. 3, the controller 36 is a controller with a proportional and integral component (PI controller). Its control deviation is formed from a target speed VSoll *, which is influenced in time in a filter block 200, and the detected actual speed VIst. The element 200 is in this case directly on the one hand the line 16 from the nominal value memory 14, on the other hand, the line 20 which transmits the actual speed fed. All other elements correspond in function to those of the first embodiment. In the filter element 200 , starting from the current vehicle speed, the predetermined target speed is given to the comparison point 32 via a filter. In the preferred exemplary embodiment, this filter is a filter of the first order, a so-called PT1 filter. The time constant of the filter depends on the speed when the controller is activated. In other advantageous exemplary embodiments, other filters can also prove to be suitable. It is essential that the filter used contains at least a first order delay. The controller 36 is designed as a controller with a proportional and integral component in order to maintain the stationary accuracy. The transient process can be set using the filter's time-dependent time constant. This takes into account the reduced acceleration capacity of the vehicle at high speeds. The switch-on conditions for the controller and setpoint value correspond to those in the exemplary embodiment according to FIG. 1. This means that if one of the switch-on conditions is present in the release block 50, the controller and the filter 200 are activated. The target speed stored in the memory element 14 is filtered based on the current actual speed with a time constant depending on the current actual speed to the target speed VSoll *, which is the basis of the control.

An example of a transient process is shown in FIG. 4. Thereafter, Fig. 4a shows the time course of the default values by the driver or by the controller SollF SollR. FIG. 4b shows the time course of the actual speed Vist, the target speed Vset and the filtered target speed Vset *. Here, too, the vehicle accelerates up to time T0 in accordance with the setpoint that is specified by the driver. The controller setpoint SollR is determined in this operating phase by the pilot control of the controller. At time T0, the controller default value falls below the driver's default value, ie the sum of the pilot control values is less than the driver target value SollF. This means that the controller and the filter are activated at time T0. From time T0, therefore, the filtered target speed VSoll *, starting from the current speed VIst at time T0, is guided to the predetermined target speed VSoll in accordance with the filter time constant. On the basis of the difference between the target speed VSoll * and the actual speed, the controller forms a correction signal for the pilot control, which at time T1 leads to the actual speed settling to the target value and a switchover to the speed controller. As in the previous exemplary embodiment, the speed controller is preferably a so-called PDT1 controller, a controller which, in addition to a proportional, also contains a delayed differential component.

In both embodiments, a uniform Behavior of the vehicle achieved under all driving conditions. It is also on a steep mountain Target speed always safely reached without the Regulatory effort increases significantly. The one used Controller structure is clear and easy to apply. The start conditions of the controller structure are simple on / off conditions, so complex Adaptation procedure for determining the starting value not are needed. Pilot control, controller and ramps are can be applied separately, therefore each Subfunction in the vehicle test can be switched off individually and the remaining are applied. The Actual acceleration calculation requires no complex Filtering because there is only one threshold at the start of the controller must be queried. Furthermore, the interference of the Driver who is particularly short below the Target speed interferes with the system (e.g. due to incorrect start values, due to unfavorable initial values of Feedforward control) largely eliminated.

In the preferred embodiment, the controller structure shown is implemented in a computer program of a microcomputer. An example of such a program is outlined as a flow chart in FIG. 5. The program part shown is processed at predetermined time intervals when the controller structure is activated.

First of all, in a first step 300 actual speed VIst, target speed VSoll, the driver default value SollF and the selected gear step GIst are read. In the subsequent step 302, the actual acceleration AIst, the difference between the target and actual speeds ΔV and the target acceleration ASoll based on this speed difference ΔV are determined as a function of the actual speed. Furthermore, the first pilot control value VW1 and the second pilot control value VW2 are calculated on the basis of the target speed VSoll and the engaged driving step GIst and on the basis of the target acceleration Aset and the inserted driving step GIst. A check is then made in query step 304 as to whether the speed difference has fallen below a predetermined value AV0. This value is very close to the target speed and in a preferred exemplary embodiment is 2 km / h. If this is the case, the speed control is activated according to step 306, which calculates a target value SollV. In the subsequent step 308, the setpoint setpoint of the actuating element is formed on the basis of the smallest value in each case from the controller preset value SollV and the driver preset value SollF, the program part ends and is repeated at the appropriate time. If the speed difference is greater than the predetermined difference ΔV0, it is checked in step 310 whether the starting conditions for the controller 36 are present. If this is not the case, according to step 312 the controller default value SollR is formed from the sum of the two pilot control values VW1 and VW2 and then in step 314 the setting target value target for the actuating element is formed from the smaller of the target values SollR and SollF, the program part is ended and added Repeated time. If the starting conditions exist according to step 310, in the subsequent step 316 the changed setpoint VSoll * becomes dependent on the speed difference ΔV, the time, the actual speed, and possibly the setpoint speed VSoll * when the ramp is terminated in the first exemplary embodiment or according to the specified filter function calculated in the second embodiment. Then, in step 318, the speed difference ΔV * supplied to the controller is formed from the difference between the target speed VSoll * and the actual speed, and in the subsequent step 320 the controller target value SollR * is calculated on the basis of the speed difference ΔV *. This takes place in the first embodiment according to a proportional controller, in the second embodiment according to a proportional integral controller. In the subsequent step 322, the controller default value SollR is calculated from the controller output value SollR * and the pilot control values VW1 and VW2 and the process continues with step 314.

In addition to the preferred application of the solution according to the invention in the context of a speed limiter solution according to the invention with the corresponding advantages also used with a speed controller, which maintains a speed specified by the driver.

Furthermore, in an advantageous embodiment not two controllers, but one controller with selectable ones Constants used, which are set depending on the operating situation or be switched off.

In both exemplary embodiments, the setpoint Vsetpoint * continuously depending on the corresponding sizes changed.

Claims (10)

1. A method for regulating or limiting the speed of a vehicle, in which a control element influencing the speed is set by at least one controller, to which a time-varying setpoint for the driving speed is fed, the at least one controller meaning the speed of the vehicle of an approximation of the speed to this setpoint, characterized in that the gradient of the setpoint supplied to the at least one controller is changed at least in accordance with the actual speed present when the controller is activated and a predetermined target speed. 2. The method according to claim 1, characterized in that a time ramp to change the target speed is given, the slope of which depends on the difference between target and actual speed and the to reaching target speed is. 3. The method according to claim 1, characterized in that the change in the setpoint according to at least one a filter function containing a delaying portion is made.   4. The method according to any one of claims 1 or 2, characterized characterized in that the controller is a controller with Is proportional. 5. The method according to any one of the preceding claims, characterized in that the actuator setting setpoint of the controller from the default value of the Controller itself and at least one of Target speed, target acceleration and speed level dependent feedforward control is formed. 6. The method according to any one of the preceding claims, characterized in that the controller is activated when the sum of the pre-control values is smaller than the default value for the control element that is specified by the driver, or if the actual acceleration of the vehicle is greater than that Target acceleration is. 7. The method according to any one of claims 1, 2 or 4 to 6, characterized in that the setpoint ramp is restarted if the default value is set by the controller (and the Pilot control) which is reached again by the driver after the driver default value has dropped below that of the controller, that the controller ramp starts from the canceled value, if the default value of the controller is the default value of the driver reached again after the driver default value increased has been. 8. The method according to claim 3, characterized in that the time constant of the filter used depends on the Speed of the vehicle is. 9. The method according to any one of claims 3 or 8, characterized characterized in that the controller is a controller with proportional and Is integral part.   10. Device for regulating or limiting the Speed of a vehicle, with at least one Regulator, which influences the speed Adjusting element, which is a time-varying Target speed is specified, and the Speed of the vehicle in the sense of an approximation of the This affects the speed at this setpoint characterized in that the slope of the at least one Setpoint supplied to the controller at least in accordance with the Activate the controller's actual speed and a predetermined target speed is changed.