DE19927223C2 - Control procedure for the high utilization of electric traction vehicles - Google Patents

Description

The invention relates to a control method for frictional engagement high utilization of electric traction vehicles according to the Preamble of claim 1.

Modern locomotives can provide traction that only can be transferred under favorable adhesion conditions.

Favorable adhesion conditions are thereby a Rei exercise number, which corresponds to the ratio of maximum traction to weight of the locomotive of about Corresponds to 0.3 to 0.5.

In the case of unfavorable adhesion conditions, excessive tensile or braking force requirements, the drive wheels are thrown or slide. Can during a gliding or spinning process considerable damage to the wheel and track caused by a rapid reduction of the (target) engine torques prevented Need to become. For high traction and braking forces even under to achieve permanent adhesion conditions become regulatory Processes for the use of high adhesion are required.

Up to now, local traffic has mainly been based on the use of rain Development process for the use of high adhesion is dispensed with. The anti-skid and anti-skid protection is due to its us may not be able to continue operation with to maintain maximum traction automatically, so that manual intervention by the driver in unfavorable adhesion conditions  [Hahn et al., 1993, "Progress in the adhesion utilization for the high-speed and Heavy duty traction ", ETR, 42 (1-2), 67-74].

Due to increasing demands in local transport have been recently however, there are also control procedures for the high-rise building used.

A longitudinal slip between the wheel and the rail is necessary to generate a tractive force in rail-bound locomotives. The tractive force is made up of the longitudinal slip forces that act on the wheels of the locomotive. Each individual longitudinal slip force F _x cannot become arbitrarily large, but is limited by the product of normal force N and the friction coefficient µ at the wheel-rail contact. The quotient of longitudinal slip force F _x by normal force N is the longitudinal force connection _x and, with a longitudinal slip s _{x, max} which is dependent on the force connection conditions _{, reaches} its maximum value given by the coefficient of friction µ ( FIG. 5).

The control procedures for the use of high traction are designed with the proviso that a longitudinal slip between the wheel and the rail is set which corresponds as closely as possible to the slip s _{x, max} at which the longitudinal traction becomes maximum.

An important problem in the case of the high utilization of the adhesion is that the slip s _{x, max is} time-variant and generally unknown. Furthermore, the longitudinal slip s _x between the wheel and the rail is also unknown, since usually no suitable measurements are carried out.

The older control procedures based on search strategies for Force utilization is common that an operation on Maximum adhesion is only possible if the engine torque is increased and decreased cyclically. While out In addition, there are some processes in the formative limit cycles  in driving mode per cycle to a spin cycle, the by quickly reducing the torque of the driving Motors must be stopped. When reducing the engine torque The power consumption of the drive is reduced within a few milliseconds by up to several 100 kW, and there are therefore additional mechanical loads on the Drive train on. This change in the electrical and mechanical loads are not desirable, but must be considered a property inherent in the methods used be accepted.

A classification feature for the classification of control procedures to the full use of the force can be derived from the strategy be inherent in the regulatory process and with those in the If necessary, the maximum traction can be achieved.

Two different classes of control strategies can be distinguished:

• 1. In the case of methods with search logic, operation at the maximum power connection is only possible if the engine torque is increased cyclically while driving and is reduced again after detection of the maximum power connection.
  The procedures with search logic differ in the criteria according to which the adhesion maximum is recognized. After the detection of the adhesion maximum, a sliding or skidding process is prevented by lowering the target engine torque M * | Mot or, if the beginning of a sliding or skidding process itself is used to detect the adhesion maximum, is ended. The target engine torque is then increased again. All of the processes have in common that even with time-invariant force-locking conditions, limit cycles are formed in the force-factor utilization.

The methods with search logic have some disadvantages, which are inherent in principle and are directly linked to the occurrence of limit cycles:

• - Cyclical excitation of resonance points in the electrical part system due to fluctuations in the power consumption of the electric drives by up to several 100 kW.
• - Cyclical excitation of resonance points in the mechanical part system due to fluctuations in engine torque of up to 50% of the nominal torque.
• - Not optimal use of the available adhesion.

The cyclical excitations of the electrical and mechanical subsystem draw z. B. increased demands on the engine control and the regulation of the four-quadrant actuator itself.

• 1. With the gradient method, a continuous drive at the maximum adhesion, that is, with constant traction, is in principle possible.
  By estimating a suitable gradient of the force-locking function or an equivalent size to this, the force-locking maximum can be detected and thus exceeding the longitudinal slip maximum force-locking s _{x, max is} prevented. The above-mentioned disadvantages of the methods with search logic, which can be attributed to the limit cycles that occur there, only occur in a weakened form in these methods. The electrical and mechanical subsystem are also excited in the gradient method, since in general an artificial excitation for estimating the gradient of the force-locking function cannot be omitted. However, the excitation is much weaker than the excitation resulting from the limit cycles in the case of methods with search logic.

DE 196 34 363 A1 describes a method for regulating the electric drive of a rail vehicle under high groove tion of the frictional connection between the wheel and rail known, at which the working point by a certain slope of the respective gene adhesion function is specified. As part of this Adhä sition control with slope controller are conditioning measures men to improve the wheel-rail contact by a Be drifted in the so-called unstable area, i.e. on which fall off the branch of the adhesion function performed.

In DE 196 34 363 A1, the gradient of the adhesion function is given by the functional relationship between the longitudinal adhesion _x and the slip speed Δν. But there are also other gradients of the adhesion function, such as the partial derivation of the longitudinal adhesion after the longitudinal slip s _x , the adhesion gradient, or according to the wheel speed ω accordingly the adhesion gradient f ω | x, instead of the derivative according to the slip speed Δν.

DE 196 34 363 A1 does not take any measures into account tion of sliding and spinning processes and for adhesion radio mentions without maximum.

DE 43 12 949 A1 describes a method for controlling and re known an electric drive of a vehicle, that can be counted among the gradient methods. With the before However, the set procedures cannot set the target values for the speed can be processed.

DE 42 25 683 C2 describes a method for wheel slip control known that an integrator in the speed control loop Includes formation of a speed setpoint.  

From the article "Examination of a procedure for High utilization of the wheel-rail adhesion Locomotives [Vogel, Ulrich, eb-electric railways 89 (1991) Pp. 285-292] is the detection of the maximum adhesion from one Sign change (= zero) of the adhesion gradient known.

A search logic is also known from DE 40 20 350 A1, which detects whether the wheelset is in stable or unstable Area of the adhesion characteristic is located.

The invention is therefore based on the object Control procedure for the high utilization of electric traction vehicles in the manner of a Gradient method, where a setpoint for the engine speed from a target set by the vehicle driver Driving speed and a predetermined target pulling force is determined for who is in steady state Traction gradient close to zero at the traction maximum recruits to ensure that the Disadvantages of the prior art avoided and the training of limit cycles completely prevented and thus an operation on Maximum adhesion  is made possible with constant traction and that continues the range of action of the control device for frictional engagement high utilization is kept as small as possible.

Under the sphere of action of the control device for power high utilization is to be understood everything that can be written by the components of a traction vehicle and the vehicle surrounding systems such as energy supply or track body and what is exposed to the consequences of a high power utilization. Such components are:

• 1.Bogie with drivetrain (including the drive converter and motor control)
• 2. Regulation of the four-quadrant controller
• 3. Passive filters in the input circuit of the transformer
• 4. Feeding electrical network
• 5. Signal systems of the infrastructure manager
• 6. Other vehicles on the network

The components mentioned under 2., 3. are designed. a. taking into account that of the operators of the rail network formulated limit values. Such limits refer to the composition of the mains electricity resulting from the Needs of the railway signaling equipment gives.

The object is achieved with the features of claim 1. The method is then characterized in that the adhesion gradient is used for a gradual change in the setpoint speed of the drive via a setpoint integrator in the speed control loop, via which the setpoint for the motor speed is determined, the setpoint acceleration being applied to the input of the setpoint integrator Dependence on the gradual change of the target speed, the control loop dynamics and the control error in the speed control loop is determined and is influenced by a separate control strategy for stabilizing the speed control loop, which in a block in the anti-reset wndup measures for a speed controller and Setpoint integrator are implemented and in which the maximum permissible nominal motor torque is determined from the specified nominal tensile force and is supplied to a limiting element between the speed controller and the drive nd sizes x _I , x _ω and parameters M _{max are} output. The adhesion maximum is detected from a zero of the adhesion gradient by methods of numerical mathematics like Newton's method. A target engine torque is provided which, in the case of time-invariant adhesion conditions, ensures a continuous drive at the maximum adhesion with maximum, constant tractive force, operation in the unstable region of the adhesion characteristic not being sought.

The regulatory process has the following advantages:

• - It allows a high traction without it to Training of limit cycles comes. It avoids the after parts of the procedure with search logic. The advantage is one Minimization of the frictional connection by the control device high utilization injected into the electrical and electrical interference mechanical subsystems of a locomotive.
• - There can be setpoints for the tractive force and the driving speed speed are processed without a modification of the Controller structure required.
• - It allows the use of different detection methods of sliding and spinning processes as well as for the detection of Traction functions without a maximum.  
• - Different adhesion gradients can be processed the, if these are in the adhesion gradient calculate. It should be borne in mind that the longitudinal traction according to common theories of longitudinal slip between wheel and Rail is largely dependent. That is the limitation "can be converted into the adhesion gradient" not procedural, but follows from the physical Conditions at the wheel-rail contact, from which rules for Selection of the necessary measured variables can be derived.

There is a universal control structure for a gradient proceed before.

Advantageous developments of the invention are in the Subclaims described.

The invention is illustrated below in a drawing Embodiment of the control method explained in more detail. It demonstrate:

Fig. 1 shows the structure diagram of the control method closing high utilization for power,

Fig. 2 is a graphical representation of the zeros of the search Kraftschlußgradienten with the Newton's method,

FIG. 3 is a graphical representation of a typical profile of the motor torque in the long term deteriorated power circuit conditions,

Fig. 4 shows the graphical representation of the normalized engine torque curve after the detection of a force-locking function without maximum and

Fig. 5 shows the graphical representation of two typical adhesion functions in rail vehicles.

With the control method according to the invention for high-efficiency adhesion according to the illustration in FIG. 1, a target engine torque can be provided, which enables continuous travel with maximum longitudinal slip or tractive force in time-variant adhesion conditions. This can be achieved if a setpoint value ω * | M for the engine speed is determined for which the frictional engagement gradient that occurs in the steady state is close to zero. The value zero is not to be regarded as an ideal setpoint in the sense of a high-pressure use, since in this case the smallest disturbances can cause a sliding or spinning process. Instead, an operation on the increasing branch of is for a high-efficiency utilization in accordance with the approach of [Engel, B., 1996, "Wear-reducing adhesion control with condition controller for electric traction drives", series 12: traffic engineering / vehicle technology (284), VDI progress reports] Traction function with a minimal traction force served as considered advantageous. A high-power use is then available if the zero point of the function, which is given by the difference between the power gradient minus the minimum force gradient, was found by suitable manipulation of the target speed ω * | M of a speed control loop.

The control method according to the invention for the high-rise building use in electric traction vehicles is a gradient method. With the method according to the invention, a continuous Nuclear ride at the traction maximum with constant traction possible, which is a basic requirement for the desired Minimization of the area of effect can be viewed.  

By evaluating a suitable gradient of the adhesion function, the method is able to detect the adhesion maximum. The adhesion maximum, at which the longitudinal slip s _{x is also} minimal, corresponds to a zero point of the adhesion gradient, as shown in FIG. 2. When calculating the step size Δs _{x, n} , which in the control loop corresponds to a change in the wheel speed by Δω _n or the motor speed by ü _G Δω _n , numerical methods can be used, such as those known when determining zeros from numerical mathematics are. Such a method is e.g. B. Newton's method ( Fig. 2 and (1)). The application of the Newtonian method has another advantage: If the train driver requests an increase in tractive force at a point in time when the axial traction is significantly smaller than the coefficient of friction µ, the target acceleration ω. * | M can be chosen greater than if the axial traction is only slightly smaller than µ. While in the first-mentioned situation the adhesion gradient is large in terms of amount, in the latter situation it is small in amount or zero at the adhesion maximum. A target acceleration ω. * | M that decreases with the magnitude of the adhesion gradient is automatically achieved in numerical methods for searching for a zero point, since the step size near the zero point is always small.

A corresponding increase in the wheel speed can be calculated according to (2) from a calculated step size Δs _{x, n} .

The second derivative of the longitudinal traction after the longitudinal slip ∂ ² _x / ∂s 2 | x (cf. (1)), since it is not known, is calculated a priori for a nominal traction function and saved as a table in the control device for the traction utilization. The gain α _N is determined in such a way that in the case of a force-locking function deviating from the nominal force-locking function, a step size Δs _{x, n} does not occur, which results in a longitudinal slip s _{x, n} on the horizontal or sloping branch of the force-locking function. The storage of a nominal adhesion function in the controller does not mean that the presented control method for the utilization of the adhesion force is not functional for other adhesion functions. Rather, the aim of introducing a nominal force-locking function is to prevent an undesired exceeding of the longitudinal slip maximum longitudinal force-locking s _{x, max} by a previously performed calculation of the gain α _N with simultaneous variation of relevant parameters of the nominal force-locking function.

Fig. 1 shows the structure diagram of the control method. The control structure is then essentially formed from the combination of the following modules: setpoint integrator 1 , steepness limiter 5 for the target driving speed, device 6 for adapting the target acceleration to the target driving speed, step control 7 , a limiting element 10 for the in the speed control loop evaluated speed error, a multiplier 11 for determining the target acceleration taking into account the speed error, block 3 for anti-reset windup measures and control strategies, steepness limiter 8 for the target tractive force, speed controller 2 , limiting element 9 for that Target torque and drive to be regulated 4 . The following working principle of the control procedure can be derived from this structure:

The central element is the setpoint integrator 1 in the speed control loop, at whose output the setpoint ω * | M for the lower-level speed control loop, which is formed in the forward branch from the speed controller 2 , the limiter 9 and the drive 4 , is available. At the input of the setpoint integrator 1 there is the set acceleration ω. * | M, which among other things becomes zero when the maximum adhesion is reached. The variable traction conditions are mainly taken into account when determining the setpoint acceleration ω. * | M with the aid of the traction gradient that is entered in the step size control 7 .

By limiting the speed error evaluated in the speed control loop to the extreme value one (limiting element 10 ), the sum of the output signals of the step size control 7 and the device 6 corresponds to the maximum desired acceleration permitted in the speed control loop under the respective adhesion conditions. By additionally evaluating this maximum target acceleration with the limited speed error by means of the multiplier 11 , the target acceleration is reduced precisely when the driving speed of the locomotive is close to the target driving speed.

When specifying a target tractive force F * | z and a target driving speed ν * | G, a minimum selection must be made. Thereafter, the target speed ω * | M is to be kept constant regardless of the target driving speed if either the tractive force derived from the target motor torque corresponds to the target tractive force F * | zd or the target motor torque corresponds to the nominal torque of the drive motor. So-called anti-reset windup (ARW) measures (cf., for example, [Böcker et al., 1986, "Nonlinear and Adaptive Control Systems", Springer, Berlin / Heidelberg]) are to be provided in order to include the mentioned situations to prevent an "overflow" of the setpoint integrator 1 . Anti-reset windup measures may also be required for speed controller 2 (depending on its internal structure). The anti-reset windup measures implemented in block 3 act on the setpoint integrator 1 (state variable x _I ) and the internal states of the speed controller 2 (state variables x _ω ) and serve to stabilize the control device. In block 3 is also determined by evaluating the predetermined target tensile force F * | z the maximum permissible nominal engine torque and supplied as a parameter M _{max of} the limiter 9 .

A speed increase Δω _{n is} determined step by step from the estimated adhesion gradient.

In a second step, taking into account the control dynamics, a time span ΔT _{n is} determined in order to determine a target acceleration ω. * | M = ü _G Δω _n / ΔT _n from the speed increase Δω _n .

When driving below the adhesion maximum, the (estimated) acceleration of the traction vehicle _{G should} be added afterwards. Otherwise, an acceleration of the engine at the maximum adhesion is not possible. The sum of the two accelerations must not exceed a maximum value set for the speed control loop from the point of view of stability. The maximum setpoint acceleration of the locomotive should be achieved if both the signal m _f assumes its maximum value and the speed error e _{ν is} greater in magnitude than e _{ν, max} . The target acceleration is given up to the sign by the value of the signal m _f .

If the values m _{f are} small, that is to say if the available longitudinal traction is fully utilized, a lowering of the setpoint for the driving speed has an insufficient effect on the set acceleration ω. * | M or the set speed ω * | M. However, a lowering of the driving speed is always possible while driving, as long as this does not have to be actively braked. For such driving situations, an adaptation of the target acceleration to the target driving speed is provided in block 6 , the output signal Δm _f ≧ 0 of which can only assume values other than zero if m _{f is} small. When designing the adaptation, it must be ensured that the sum of m _f and Δm _f does not exceed the maximum value of m _f and thus the maximum permissible setpoint acceleration.

After the detection of a sliding or spinning process or a force-locking function without a maximum, a special control strategy for stabilizing the drive 4 for the desired engine torque is required, which are implemented in block 3 . Rapid changes over time in the target engine torque are generally to be avoided in order to minimize the range of effectiveness of the control device for the use of positive traction.

For the detection of gliding and spinning is a too provide additional detector, its output signal SSD here was accepted as binary.

After the detection of a sliding or spinning process, the maximum engine torque M _{max is} reduced with the aid of a control strategy, and thus the amount of the desired torque M * | Mot is also reduced with the aid of the limiter 9 , and the end of the sliding or Spin process brought about. While the torque M _max is being reduced, the control device is to be stabilized with the anti-reset windup measures implemented in block 3 by manipulating the state variables x _I and x _ω . If the end of a sliding or spinning process has been detected, the motor torque must be increased again in controlled operation in order to achieve a pull or braking force that is as little as possible less than the force that was achieved before the sliding or spinning process began . It is important to ensure that the sliding or spinning process may have been triggered by a long-term deterioration in the adhesion conditions.

In Fig. 3 is schematically shown for the driving operation, such as reduction of the engine torque can be made. It was assumed that at time t = 0.5 s a second spin process occurred due to long-term deterioration of the adhesion conditions. The torque M _{Mot, 2} is calculated before geous by evaluating the time period Δt _SSE , which indicates the time interval between two sliding or spinning processes. The torque M _{Mot, 2} is to be selected the smaller, the smaller the time span Δt _SSE . One possibility is:

The torque M _{Mot, min} represents the engine torque that leads to a pulling force even under the most unfavorable adhesion conditions, without a renewed sliding or spinning process. The factor r _{M represents} the proportion to which the amount of the target torque is increased after a sliding or spinning process in controlled operation.

If the current adhesion function has no maximum, it can, for. B. while driving, with constant traction to a continuous, magnification of the longitudinal slip and thus an undesirable increase in friction come in contact. It is therefore (optionally) to provide a suitable detector for the detection of a force-locking function without a maximum, the output signal FHD of which was assumed to be binary. After an operation in the saturation range of the adhesion function has been detected, e.g. B. temporarily reduces the engine torque while driving by lowering the maximum torque M _max ; As with the detection of a sliding or spinning process, the control device is to be stabilized with the anti-reset windup measures implemented in block 3 . The reduction is intended to achieve a new operating point on the traction function with greater longitudinal slip with almost the same longitudinal traction.

A possible, normalized course of the engine torque after the detection of a force-locking function without a maximum is shown in FIG. 4. The engine torque does not reach its original value for t <1.3 s, but is slightly below it to ensure a new operating point on the increasing branch of the adhesion function. The above-mentioned anti-reset wind-up measures are activated for 0.5 s ≦ t ≦ 1.3 s as part of a control procedure for the use of high levels of force.

Since the target values for the driving speed or the tractive force act on quantities that accelerate the vehicle can determine a usually existing limitation of the Jerks with slope limiters in the signal paths of the target values can be achieved.

If there is no setpoint for the vehicle speed, it must be set according to the sign of the setpoint force F * | z:

List of reference symbols

1

Setpoint integrator

2nd

Speed controller

3rd

block

4

drive

5

Slope limiter

6

contraption

7

Step size control

8th

Slope limiter

9

Limiting element

10th

Limiting element

11

multiplier
SSD output signal
FHD output signal
v

       * | G     

Target driving speed
F

       * | z     

Target pulling force
(Estimated) acceleration of the locomotive
ω

       . * | M     

Target acceleration
_G

(Estimated) speed of the locomotive
ω

       * | M     

Setpoint engine speed
M

       * | Mot     

Target engine torque
M _max

Torque
M _{Mot, min}

Torque
Adhesion gradient
s _x

Longitudinal slip

Claims (6)

1. Control method for the traction utilization of electric traction vehicles in the manner of a Gradientverfah rens, wherein a target value for the engine speed is determined from a predetermined driving speed specified by the driver and a predetermined target traction, for which there is a traction gradient close to the value in the steady state Sets zero in the adhesion maximum, characterized in that

• - The adhesion gradient for a gradual change in the target speed of the drive ( 4 )
• - A setpoint integrator ( 1 ) is used in the speed control loop, via which the setpoint for the engine speed is determined, wherein
• - At the input of the setpoint integrator ( 1 ), the setpoint acceleration is applied, which is determined as a function of the gradual change in the setpoint speed, the control loop dynamics and the control error in the speed control loop and is influenced by a separate control strategy for stabilizing the speed control loop, which in a block ( 3 ) in which anti-reset wind-up measures for a speed controller ( 2 ) and the setpoint integrator ( 1 ) are implemented and in which the maximum permissible nominal motor torque is determined from the specified nominal tractive force and a limit tion element ( 9 ) between the speed controller ( 2 ) and the drive ( 4 ) is supplied, implemented and output as status variables (x _I , x _ω ) and as parameters (M _max ),
• - The maximum adhesion from a zero of the adhesion gradient is detected by methods of numerical mathematics such as Newton's method (( 2 )) and
• - A target engine torque is provided, which ensures a continuous drive at the maximum force with maximum, constant traction force in time-invariant adhesion conditions, operation in the unstable area of the adhesion characteristic is not aimed.

2. The method according to claim 1, characterized in that in the block ( 3 ) for anti-reset windup measures Lich additional control strategies for the engine torque during a sliding or skidding process and / or in a detected operation in the saturation range of a force-locking function without Are implemented as a maximum and are output as state variables for the setpoint integrator ( 1 ) and the speed controller ( 2 ) as well as the maximum permissible setpoint engine torque as parameters to the limiting element ( 9 ). 3. The method according to claim 1, characterized, that in the absence of an operationally specified setpoint for the driving speed a target value from the target train force is determined in such a way that greater for target tensile forces or zero the target driving speed is equal to the ma ximal operational speed of the drive corresponds to the vehicle and for target tensile forces less than zero the target driving speed is set to zero.   4. The method according to claim 1, characterized in that a steepness limiter ( 5 , 8 ) in the signal paths for the setpoints of the driving speed and the tractive force is used to limit the jerk. 5. The method according to claim 1, characterized, that a permanent deterioration in the adhesion conditions by evaluating the time period between two successive gliding or spinning processes detected and in the control strategy for the engine torque a sliding or spinning process is taken into account. 6. The method according to claim 1, characterized in that the acceleration of the locomotive is taken into account when determining the gradual change in the target speed of the drive ( 4 ).