DE102007018449A1 - Method for anti-slip regulation of hydrostatic traction drive, involves determining wheel speed of drive wheels with sensor arrangement - Google Patents

Abstract

The method involves determining the wheel speed of the drive wheels with a sensor arrangement. A slip of a drive wheel is determined from the wheel speed and a corresponding slip signal is emitted. The displacement of the hydraulic motor belonging to drive wheel and the torsional moment is reduced after stipulation of the slip signal. An independent claim is also included for a hydrostatic vehicle drive.

Description

The The invention relates to a method for anti-slip control of hydrostatic Vehicle drives according to claim 1 and a hydrostatic vehicle drive with an anti-slip Regulation according to claim 6th

Classical Anti-slip control systems are designed to prevent the spinning of wheels on a vehicle by torque reduction on the affected wheel so as far as possible to avoid. Wheel slip is one of many parameters such as Underground, tires, speed, speed u. v. a. dependent disturbance variable, at the controller can only intervene if already a significant control difference is present. In the technical literature, such control systems become common as disturbance control systems designated.

In hydrostatic drives drives an internal combustion engine (BKM), typically a diesel engine, one or more hydraulic pumps, which in turn supply several hydraulic motors. The hydraulic motors are each a drive wheel or at least one drive axle assigned. As a control variable for the anti-slip regulation serves traditional the displacement of the hydraulic motors. When the sensor system is spinning determines the swallowing volume of the affected person Retracted drive wheel associated hydraulic motor. This reduces its torque, the so that only to a lesser extent on the Output side available stands, which counteracts the spin of this wheel.

One Such control system is relatively unstable, in particular leads the Reduction of the displacement of the hydraulic motor to allow it at the same time the system pressure rises because the pump is still promotes an equal volume flow. From the increased system pressure again results in an increase of the total torque and an acceleration of the vehicle, the a new, additional Disturbance for the control system forms.

Of the The present invention is based on the object of anti-slip System with improved disturbance reduction for one provide hydrostatic drive.

According to the invention this object is achieved by a method for anti-slip control of a hydrostatic drive, wherein the drive comprises at least one driven by an internal combustion engine pump and a plurality of driven by the at least one hydraulic motors, which are respectively associated drive wheels or drive axles, the method following Steps includes:
With one sensor arrangement, the wheel speed of the drive wheels is determined. From the wheel speeds a slip of a drive wheel is determined and issued a corresponding slip signal. In accordance with the slip signal, the displacement of the drive wheel belonging to the hydraulic motor and thus the torque is reduced. At the same time, the overall torque of all drive wheels determining the advance is reduced in accordance with the slip signal.

Prefers the reduction of the total torque of all drive wheels takes place Reduction of the pumped volume flow or in that the speed of the internal combustion engine is reduced becomes. In another version of the inventive concept, the total torque of all drive wheels by changing the translation ratio a transmission can be reduced. Likewise, combinations of these are applicable with advantage, offers particular advantages in particular embodiment, in which both the flow rate of the pump and that of the internal combustion engine generated torque, ie, for example, the speed, withdrawn become. In this case, the control is preferably designed that the control signal for reducing the torque of the internal combustion engine leads the way to reduce the pump current.

According to the invention Task also by a hydrostatic vehicle drive with at least a driven by an internal combustion engine pump and several solved by the pump driven hydraulic motors, wherein at least two drive wheels or Each drive axle is assigned a hydraulic motor and an anti-slip control is provided, which includes a sensor for detecting a spin Rades identifies and the torque of the associated hydraulic motor after proviso reduced by the sensor output slip signal, as well as a Device which, at the same time the total torque of all drive wheels after proviso the slip signal is reduced.

The Reduction of the total torque can be achieved by a traction drive control be made as specified the slip signal the pump flow rate, the torque of the internal combustion engine or the gear ratio of a Gear reduced

Further Features and advantages of the invention will become apparent from the following Description of the figures.

It demonstrate:

1A . 1B : An embodiment with a pump and three hydraulic motors;

2A . 2 B : Another embodiment according to the invention;

3 : A block diagram of the anti-slip control system

4 : A schematic representation of the characteristic of the anti-skid control waveforms over time.

In 1 is on the part sheets 1A and 1B an embodiment of the anti-slip control system according to the invention shown using the example of a traction drive with control electronics.

1A shows the drive control 17 , the anti-slip control unit 18 and the internal combustion engine 1 , which has its own control system and is usually operated by means of accelerator and / or forward / reverse lever. In 1 only the circuit parts relevant for the anti-slip control are shown here; the basic vehicle control is conventional. The units 1 . 17 . 18 are over a CAN bus 19 (Controller Area Network), via which the computing units exchange the relevant control variables for pump reduction and BKM reduction. In each of the units, this is a CAN driver 20 and corresponding bus contacts 13 (CAN shielding 14 , CAN high 15 and CAN low 16 ) provided to both the flow rate of the pump 2 as well as to be able to control the BKM speed in accordance with the determined wheel slip.

1B represents the vehicle with the interfaces to sensors and actuators. The pump 2 is mechanically, for example via a transmission of the internal combustion engine (BKM) 1 driven. The one from the pump 2 funded volume flow, is via the drive control 17 by means of the pump adjustment unit 10 regulated. The adjustment of the pump 2 takes place hydraulically by means of the valve unit 9 that with the drive control 17 over the control lines 25 is connected and electronically controlled by this. The feedback of the pump speed is carried out by means of the speed sensor 8th over the measuring line 26 for drive control 17 , which closes this loop.

The pump 2 supplies the hydraulic motors 3 . 4 . 5 , Which are, for example, designed as oblique axis engines and of which in each case one of the rear wheels and one of the front axle 6 assigned. In the same way, a plurality of pumps, for example, one each for each hydraulic motor may be present. Likewise, a separate hydraulic motor can be provided for each of the front wheels.

The wheel speed is in the example shown on the output speeds of the hydraulic motors 3 . 4 . 5 by means of the speed sensors 7 measured. The anti-slip control unit 18 receives its sensor signals and determines therefrom in the manner described below target speed and slip. The determined slip value serves on the one hand to control the absorption volume of the hydraulic motors 3 . 4 . 5 that communicate over the associated valve units 11 and adjusting devices 12 be adjusted, and on the other hand to the aforementioned pump or BKM reduction.

The control system works in such a way that when slip occurs, the displacement of the affected hydraulic motor is reduced to reduce its torque. At the same time, the slip value is transmitted via the CAN bus 19 to the drive control unit 17 and to the internal combustion engine 1 forwarded. About the drive control unit 17 If the slip occurs, the volume flow delivered by the pump P2 is reduced. In addition, the BMK speed is reduced to counteract with these measures the spinning of the drive wheels.

Another embodiment of the invention is in 2 represented, wherein the reference numerals for the same components has been retained. In contrast to 1A Here the controlled variables are not transmitted via the CAN bus between the drive control 17 and the anti-slip regulation 18 replaced. Rather, these two units are logically combined to form a control unit. Only the internal combustion engine 1 remains a stand-alone device. The data for the BKM reduction will therefore continue to be transmitted via the CAN bus. The operation of the anti-slip regulation is the same as in 1 , to the description of which reference is made.

3 shows the basic sequence of the anti-slip control according to the invention, for example, with two rear drive wheels plus a driven front axle and three associated hydraulic motors whose intake volume via an adjustment and appropriately designed actuators 33 is regulated. For this purpose, the speeds or speeds of the drive wheels each have suitable sensors 7 detected. From the usually different wheel speeds is initially a reference value 27 determined, for example, may be the slowest of the measured, non-zero speeds. This reference value then specifies the target speed for all wheels.

The hatching value determination 28 done by Difference between the actual speeds of the drive wheels and the target speed and is in the example of 3 in percent of the actual speed to a controller, for example a PID controller 29 output. Here, a predefinable tolerance value 30 which takes into account a maximum permissible deviation from the setpoint speed (maximum permitted speed 31 ) certainly. The higher the permitted tolerance, the less a controlled variable is formed. If the maximum permitted wheel speed is exceeded, a compensation by the anti-slip control system takes place. The PID controller 29 There is an amplifier 32 a corresponding manipulated variable to the actuator 33 the adjustment of the affected hydraulic motor. The type and settings of the controller can be configured very differently and adapted individually to the respective vehicle type and their requirements.

According to the invention now the control variables for the hydraulic motors with the BKM and pump control 34 , that is linked to the propulsion of the vehicle, which by the volume flow delivered by the pump, the speed of the internal combustion engine 1 , and / or the gear ratio is determined. For this purpose, the controlled variables are supplied to a range adaptation with regard to their start and end values and the manipulated variables at the actuators 35 . 36 adapted to the pump or the internal combustion engine. Depending on the vehicle and the area of application, the pump may be partially or completely returned to the pump setpoint values, but in the case of a 100% return, the vehicle usually comes to a standstill. As practicable value, a control range R of 0% <R ≤ 50% has proven useful in practice. Here, the responsible for the propulsion total torque is reduced accordingly, so that the spinning of individual wheels can be compensated in an advantageous manner.

Since according to the invention the anti-slip control superimposed on the driving situation dependent and comparatively sluggish drive control / regulation of pump and engine, an adjustment in terms of the time constant is further required, for example. By integration over time in a respective actuators 35 . 36 upstream filter 37 can be done. Good results are obtained if here also a PID controller is provided, which is followed by a first-order filter.

A particularly advantageous embodiment is obtained if, when slip occurs, both the volume flow conveyed by the pump and the rotational speed of the internal combustion engine are reduced. However, in the setpoint reduction of the internal combustion engine usually occurs a delay in the system reaction when the required power is to be retrieved again, for example, if this charge pressures of turbochargers o. The like. Must be generated, which naturally take time to the engine power after rebuild a setpoint reduction. It has proven to be advantageous if the signal for the engine reduction leads the pump reduction something, which by appropriate design of the respective actuators 35 . 36 upstream filter 37 can be easily realized.

In 4 are characteristic waveforms plotted over time, which can be easily removed in practice on the real circuit and, for example, can be used to identify and verify the control behavior of the invention. The solid curve represents the slip 21 which is essentially the curve of the wheel speed 22 follows. Dotted is further the inverted volume flow of the pump thus the pump reduction 24 reproduces. As the diagram shows, the measured reduction of the pump current follows exactly the course of the wheel slip. The same applies to the swallow volume 23 the affected hydraulic motor, which is shown in the dashed curve. The curves show that with a reduction of the hydraulic motor displacement in conjunction with a reduction in the volume flow delivered by the pump, ie a corresponding reduction in the total torque of the vehicle drive, an efficient anti-slip control results.

1

Internal combustion engine (BKM)

2

hydraulic pump

3

hydraulic motor (Front)

4

hydraulic motor (left rear wheel)

5

hydraulic motor (right rear wheel)

6

Front

7

Speed sensor (Hydraulic motor output axis)

8th

Speed sensor (Pump)

9

valve unit for electronic pump adjustment

10

Pump-control device

11

valve unit for electronic Adjustment of a hydraulic motor

12

adjustment (Hydraulic motor)

13

bus contacts

14

Can shielding

15

Can High

16

Can low

17

Drive control unit

18

Anti-skid control unit

19

CAN bus

20

CAN driver

21

slippage

22

wheel speed

23

Engine displacement

24

Flow reduction (Pump)

25

control lines

26

Measurement line

27

determination the reference value

28

Slip value determination

29

PID controller

30

tolerance

31

Determination "max. allowed Speed"

32

amplifier

33

actuators (Hydraulic motors)

34

BKM and pump control

35

actuator (BKM)

36

actuator (Pump)

Claims (9)

Method for anti-slip control of a hydrostatic drive with at least one of an internal combustion engine ( 1 ) driven pump ( 2 ) and several of the at least one pump ( 2 ) driven hydraulic motors ( 3 . 4 . 5 ), which are respectively assigned to drive wheels or drive axles, with the following steps: each having a sensor arrangement ( 7 ) determines the wheel speed of the drive wheels; From the wheel speeds a slip of a drive wheel is determined and a corresponding slip signal ( 28 ) issued; in accordance with the slip signal ( 28 ) the displacement of the drive wheel belonging to the hydraulic motor ( 3 . 4 . 5 ) and thus reduces its torque; At the same time, the total torque of all drive wheels is reduced in accordance with the slip signal. The method of claim 1, wherein the total torque all drive wheels by withdrawal of the pump flow rate is reduced. Method according to Claim 1 or 2, in which the total torque of all driving wheels is controlled by regulating the internal combustion engine ( 1 ) is reduced by their speed is reduced. Method according to one of claims 1 to 3, wherein the Total torque of all drive wheels by change the translation ratio a transmission is reduced. Method according to one of claims 1 to 4, wherein the total torque of all drive wheels both by withdrawal of the pump flow rate and by reducing the speed of the internal combustion engine ( 1 ) is reduced, wherein the actuating signal for reducing the rotational speed of the internal combustion engine ( 1 ) leads the way to reduce the pump current. Hydrostatic vehicle drive with - at least one of an internal combustion engine ( 1 ) driven pump ( 2 ) and several of the pump ( 2 ) driven hydraulic motors ( 3 . 4 . 5 ), wherein at least two drive wheels or drive axles in each case a hydraulic motor is assigned, - an anti-slip regulation ( 3 ), which has a sensor ( 7 ) for detecting a spinning wheel identifies and the torque of the associated hydraulic motor ( 3 . 4 . 5 ) according to one of the sensors ( 7 ) reduced slip signal - a device that also reduces the total torque of all drive wheels in accordance with the slip signal. Hydrostatic vehicle drive according to claim 5, in which a traction control is provided, which, in accordance with the Slip signal controls the pump adjustment such that the pump flow rate is reduced. Hydrostatic vehicle drive according to claim 5 or 6, in which a traction drive control is provided which, in accordance with the slip signal, the rotational speed of the internal combustion engine ( 1 ) reduced. Hydrostatic vehicle drive according to one of claims 5 to 7, in which a traction control is provided, the after Stipulation of Slip signal the transmission ratio of a Gear reduced.