Method and control system for controlling an electronically regulated brake actuating system

• US 20040080208A1
• Filed: 03/27/2003
• Published: 04/29/2004
• Est. Priority Date: 09/27/2000
• Status: Active Grant

• Current Assignee: Continental Teves AG & Co. OHG (Continental AG)
• Original Assignee: Continental Teves AG & Co. OHG (Continental AG)
• Inventors: Böhm, J?uuml;rgen, Giers, Bernhard, Schmidt, Robert, Ullrich, Thorsten
• Granted Patent: US 6,851,764 B2
• Time in Patent Office: Days
• US Class Current: 303/20
• CPC Class Codes: B60T 13/686 in hydraulic systems or parts thereof
• CPC Class Codes: B60T 8/36 including a pilot valve responding to an electromagnetic force
• CPC Class Codes: B60T 8/4081 Systems with stroke simulating devices for driver input B60T8/4077 takes precedence

Abstract

The invention discloses methods and control systems for controlling an electronically controllable brake actuating system for automotive vehicles, with a depressurized pressure medium supply reservoir (4), with at least one pressure source (20) which can be controlled by an electronic control unit (32), said pressure source being used to apply pressure to the wheel brakes (7,8,9,10) of the vehicle, with pressure sensors and pressure control valves (inlet valve 17,18; outlet valve 27,28) being associated with said wheel brakes, said pressure control valves being controllable in an analog manner by means of an electric variable in dependence on the differential pressure applied to them and connecting the wheel brakes (7-10) to the pressure source (20) in a pressure increase phase, being closed or becoming closed in a pressure maintenance phase and connecting the wheel brakes (7-10) to the pressure medium supply reservoir (4) in a pressure reduction phase.

To permit adapting the dependence between the electric variable and the differential pressure to manufacture spread and aging effects, as well as to changing environmental conditions, the present invention arranges for the electric variable in the pressure control valve (inlet valve 17, 18; outlet valve 27, 28) that is to be identified to be slowly varied in the pressure maintenance phase until a noticeable pressure change takes place in the wheel brake (7, 8) associated with said pressure control valve (inlet valve 17, 18; outlet valve 27, 28), whereupon the dependence of the electric variable on the differential pressure is corrected.

Claims

1. Method for controlling an electronically controllable brake actuating system for automotive vehicles, with a depressurized pressure medium supply reservoir (4), with at least one pressure source (20), which can be controlled by an electronic control unit (32), said pressure source being used to apply pressure to the wheel brakes (7,8,9,10) of the vehicle, with pressure sensors and pressure control valves (inlet valve 17,18;

outlet valve 27,28) being associated with said wheel brakes, said pressure control valves being controllable in an analog manner by means of an electric variable in dependence on the differential pressure applied to them and connecting the wheel brakes (7-10) to the pressure source (20) in a pressure increase phase, being closed or becoming closed in a pressure maintenance phase and connecting the wheel brakes (7-10) to the pressure medium supply reservoir (4) in a pressure reduction phase,

characterized in that the electric variable in the pressure control valve (inlet valve 17, 18;

outlet valve 27, 28) to be identified is slowly varied in the pressure maintenance phase until a noticeable pressure variation takes place in the wheel brake (7, 8) associated with said pressure control valve (inlet valve 17, 18;

outlet valve 27, 28), whereupon the dependence of the electric variable on the differential pressure is corrected.

2. Method as claimed in claim 1,

characterized in that the pressure control valves (inlet valve 17, 18;

outlet valve 27, 28) are designed as valves that are closed in their inactive condition, and in that the variation of the electric actuating variable is an increase based on a value that is below the value necessary for opening the pressure control valve (inlet valve 17, 18;

outlet valve 27, 28).

3. Method as claimed in claim 1,

characterized in that the pressure control valves (outlet valve 27, 28) used for pressure reduction are designed as valves that are open in their inactive condition, and in that the variation of the electric actuation variable is a reduction based on a value that is above the value necessary for retaining the pressure control valve (outlet valve 27, 28) in the closed condition.

4. Method as claimed in any one of claims 1 to 3,

characterized in that the variation of the electric variable occurs in defined driving situations.

5. Method as claimed in any one of claims 1 to 3,

characterized in that the variation of the electric variable occurs during vehicle standstill or in a defined range of the vehicle speed.

6. Method as claimed in any one of claims 1 to 3,

characterized in that the variation of the electric variable occurs at a low variation speed of a braking pressure nominal value.

7. Method as claimed in any one of claims 1 to 3,

characterized in that the variation of the electric variable occurs after a minimum duration of the pressure maintenance phase.

8. Method as claimed in any one of claims 1 to 7,

characterized in that the variation of the electric actuation variable is discontinued when the difference between nominal pressure and actual pressure leaves a predetermined tolerance range.

9. Method as claimed in claim 8,

characterized in that the limits of the tolerance range are fixed in dependence on the vehicle speed.

10. Method as claimed in any one of claims 1 to 9,

characterized in that the pressure control valves (17, 18;

27, 28) are designed as electromagnetically controllable valves, and in that the electric variable is an electric current (I) being supplied to the electromagnetic drive.

11. Method as claimed in any one of claims 1 to 9,

characterized in that the pressure control valves are configured as piezoelectrically controllable valves, and in that the electric variable is an electric voltage (U) being applied to the piezoelectric drive.

12. Method as claimed in any one of claims 1 to 11,

characterized in that the pressure variation in the wheel brake (7, 8) associated with the pressure control valve (17, 18) during the variation of the electric variable is observed cyclically in a time window (T_w) and the maximum pressure value is determined in each case which, in turn, is taken into account for determining a detection threshold (E) for the pressure change at the outlet of the pressure control valve (inlet valve 17, 18) used for pressure increase.

13. Method as claimed in any one of claims 1 to 11,

characterized in that the pressure variation in the wheel brake (7, 8) associated with the pressure control valve (27, 28) during the variation of the electric variable is observed cyclically in a time window (T_w), and the minimum pressure value is determined in each case which, in turn, is taken into account for determining a detection threshold (E) for the pressure change at the inlet of the pressure control valve (outlet valve 27, 28) used for pressure reduction.

14. Method as claimed in claim 12,

characterized in that a detection threshold E in the window i is defined according to the formula

E=Max(p)|window(i−

1)+∈

,

where ∈

is a process parameter taking into account valve leakage and malfunctions of the pressure sensor (30, 31) sensing the pressure variation.

15. Method as claimed in claim 14,

characterized in that opening of the pressure control valve (inlet valve 17, 18) is inferred when the pressure value at the outlet of the pressure control valve (inlet valve 17, 18) exceeds the detection threshold (E) in the time window (i).

16. Method as claimed in claim 13,

characterized in that a detection threshold E in the window i is defined according to the formula

E=Max(p)|window(i−

1)−

∈

,

where ∈

is a process parameter taking into account valve leakage and malfunctions of the pressure sensor (30, 31) sensing the pressure variation.

17. Method as claimed in claim 16,

characterized in that opening of the pressure control valve (outlet valve 27, 28) is inferred when the pressure value at the inlet of the pressure control valve (outlet valve 27, 28) drops below the detection threshold (E) in the time window (i).

18. Method as claimed in any one of claims 12 to 17,

characterized in that at time (t_detect), when the pressure value at the outlet of the pressure control valve (inlet valve 17, 18) used for pressure increase or at the inlet of the pressure control valve (outlet valve 27, 28) used for pressure reduction exceeds or falls below the detection threshold (E), a point of time is calculated according to the formula

t_react=t_detect−

τ

where τ

designates the offset in time between the reaction of the pressure control valve caused by the actuation and the detection of this reaction by way of the change in pressure.

19. Method as claimed in claim 18,

characterized in that the offset in time (τ

) is determined in dependence on a signal characterizing the viscosity of the pressure medium.

20. Method as claimed in any one of the preceding claims 10 and 12 to 19,

characterized in that the dependence of the actuating current I(Δ

p) on the differential pressure (Δ

p) is corrected according to the formula

I(Δ

p)^new=I(Δ

p)^old·

(1−

λ

)+λ

·

I_react,

where I_react designates the actuating current value corresponding to the change in pressure in the wheel brake (7, 8) associated with the pressure control valve (inlet valve 17, 18;

outlet valve 27, 28) at time (t_react), I(Δ

p)^old designates the value of the dependence of the actuating current I(Δ

p) on the differential pressure (Δ

p) in the present operating point (Δ

p) before the correction (adaption) is carried out, and I(Δ

p)^new designates the value of the dependence of the actuating current I(Δ

p) on the differential pressure (Δ

p) after the correction (adaption) is carried out, and the adaption rate λ

should be selected from the interval (0, 1].

21. Method as claimed in any one of the preceding claims 11 to 19,

characterized in that the dependence of the voltage U(Δ

p) being applied on the differential pressure (Δ

p) is corrected according to the formula

U(Δ

p)^new=U(Δ

p)^old·

(1−

λ

)+λ

·

U_react,

where U_react designates the actuating voltage value corresponding to the change in pressure in the wheel brake associated with the pressure control valve at time (t_react), U(Δ

P)^old designates the value of the dependence of the actuating voltage U(Δ

p) on the differential pressure (Δ

p) in the present operating point (Δ

p) before the correction (adaption) is carried out, and U(Δ

p)new designates the value of the dependence of the actuating voltage U(Δ

p) on the differential pressure (Δ

p) after the correction (adaption) is carried out, and the adaption rate λ

shall be selected from the interval (0, 1].

30. A control system for implementing the method for actuating an electronically controllable brake actuating system as claimed in any one of the preceding claims,

characterized in that a pressure controller (40) is provided to which are sent, as input quantities, a nominal pressure value (P_nom) that shall be applied to one of the wheel brakes (7, 8) of the vehicle, an actual pressure value (P_act) that is applied to one of the wheel brakes (7, 8) of the vehicle, as well as the hydraulic differential pressure value (Δ

p) prevailing at the pressure control valve (17, 18;

27, 28) under review and having an output quantity that is the nominal value (I_nom or U_nom) of the electric variable used to actuate the pressure control valve (17, 18;

27, 28), and in that there is provision of means (45, 46) for the correction (adaption) of the dependence on the electric variable (I or U) on the differential pressure value (Δ

p).

31. Control system as claimed in claim 30,

characterized in that the pressure controller (40) comprises a linear controller (41), a pilot control module (42), and a correction module (45, 46), and the deviation (Δ

P_R) produced from the nominal pressure value (P_nom) and actual pressure value (P_act) is sent to the linear controller (41) as an input quantity, while a signal representative of the hydraulic differential pressure (Δ

p) prevailing at the pressure control valve (17, 18;

27, 28) under review is sent to the pilot control module (42), with said pilot control module (42) generating a pilot control value (I_nom,V;

U_nom,V) of the electric variable (I, U) used to actuate the pressure control valve (17, 18;

27, 28) that corresponds to the opening point of the pressure control valve (17, 18;

27, 28) and is added to the output quantity (I_nom,L;

U_nom,L) of the linear controller (41) for producing the nominal value (I_nom;

U_nom) of the electric variable used to actuate the pressure control valve (17, 18;

27, 28), and with the actual pressure value (P_act) and the differential pressure (Δ

p) prevailing at the pressure control valve (being identified) under review being sent as input quantities to the correction module (45, 46) and the output quantity (K₁,K₂) influencing the performance of the pilot control module (42).

32. Control system as claimed in claim 31 for implementing the method for actuating an electronically controllable brake actuating system as claimed in any one of claims 1 to 21,

characterized in that the output quantity (K₁) of the correction module (45) is defined as a difference:

K₁=I(Δ

p)^new−

I(Δ

p)^old or K₁=U(Δ

p)^new−

U(Δ

p)^old

where I(Δ

p)^old or U(Δ

p)^old designates the value of the dependence of the electric actuation variable I(Δ

p) or U(Δ

p) on the differential pressure (Δ

p) in the present operating point (Δ

p) before the correction (adaption) is carried out, and I(Δ

p)^new or U(Δ

p)^new designates the value of the dependence of the electric actuation variable I(Δ

p) or U(Δ

p) on the differential pressure (Δ

p) after the correction (adaption) is carried out.

33. Control system as claimed in claim 31 for implementing the method for actuating an electronically controllable brake actuating system as claimed in any one of claims 18 to 24,

characterized in that the nominal pressure value (P_nom) is additionally sent as an input quantity to the correction module (46), and in that its output quantity K₂=−

Δ

I is derived from the comparison of the detected number of the actuation processes (N_red, N_incr) with a maximum allowed numerical value (N_red*, N_incr*), and the dependence of the electric variable is reduced when the maximum allowed numerical value (N_red*,N_incr*) is exceeded.

22. Method for controlling an electronically controllable brake actuating system for automotive vehicles, with a depressurized pressure medium supply reservoir (4), with at least one pressure source (20) which can be controlled by an electronic control unit (32), said pressure source being used to apply pressure to the wheel brakes (7,8) of the vehicle, with pressure control valves (inlet valve 17,18;

outlet valve 27,28) being associated with said wheel brakes, said pressure control valves being controllable in an analog manner by means of an electric variable in dependence on the differential pressure applied to them and connecting the wheel brakes (7,8) to the pressure source (20) in a pressure increase phase, being closed or becoming closed in a pressure maintenance phase, and connecting the wheel brakes (7, 8) to the pressure medium supply reservoir (4) in a pressure reduction phase,

characterized in that the frequency of the actuation processes of the pressure control valves (inlet valve 17, 18;

outlet valve 27, 28) is determined and taken into consideration according to a nominal pressure variation to be controlled in the wheel brakes (7, 8) for the correction (reduction) of the dependence of the electric variable (I, U) on the differential pressure (Δ

p).

23. Method as claimed in claim 22,

characterized in that the number (N_red) of the actuation processes of the pressure control valve (outlet valve 27, 28) used for pressure reduction is determined during a pressure increase phase of the nominal pressure variation of the duration (T_incr), and in that an excessive actuation of the pressure control valve (inlet valve 17, 18) used for pressure increase is inferred from the exceeding of a threshold value.

24. Method as claimed in claim 22,

characterized in that the number (N_incr) of the actuation processes of the pressure control valve (inlet valve 17, 18) used for pressure increase is determined during a pressure reduction phase of the nominal pressure variation of the duration (T_incr), and in that an excessive actuation of the pressure control valve (outlet valve 27, 28) used for pressure reduction is inferred from the exceeding of a threshold value.

25. Method as claimed in claim 23 or 24,

characterized in that the number determined (N_red, N_incr) is compared to a maximum allowed numerical value (N_red*, N_incr*) that is produced according to the formula

N_red*=f_B·

T_incr or N_incr=f_B·

T_red

where f_B is a maximum allowed actuation frequency and T_inc, T_red designates the duration of the phase of rise or fall of the pressure, and in that an excessive actuation of the pressure control valve (inlet valve 17, 18, outlet valve 27, 28) used for pressure increase or reduction is inferred from the exceeding of the maximum allowed numerical value (N_red*, N_incr*)

26. Method as claimed in claims 22 to 25,

characterized in that the pressure control valves (17,18;

27,28) are designed as electromagnetically controllable valves, and in that the electric variable is an electric current being supplied to the electromagnetic drive.

27. Method as claimed in claims 22 to 25,

characterized in that the pressure control valves are configured as piezoelectrically controllable valves, and in that the electric variable is an electric voltage being applied to the piezoelectric drive.

28. Method as claimed in claims 25 and 26,

characterized in that the correction of the dependence of the actuating current I(Δ

p) on the differential pressure (Δ

p) is carried out according to the formula

I(Δ

p)^new=I(Δ

p)^old−

Δ

I,

where I(Δ

p)^old designates the value of the dependence of the actuating current I(Δ

p) on the differential pressure (Δ

p) in the present operating point (Δ

p) before the correction (reduction) is carried out, and I(Δ

p)^new designates the value of the dependence of the actuating current I(Δ

p) on the differential pressure (Δ

p) after the correction (reduction) is carried out.

29. Method as claimed in claims 25 and 27,

characterized in that the correction of the dependence of the voltage U(Δ

p) to be applied on the differential pressure (Δ

p) is carried out according to the formula

U(Δ

p)^new=U(Δ

p)^old−

Δ

U,

where U(Δ

P)^old designates the value of the dependence of the actuating voltage U(Δ

p) on the differential pressure (Δ

p) in the present operating point (Δ

p) before the correction (reduction) is carried out, and U(Δ

p)^new designates the value of the dependence of the actuating voltage U(Δ

p) on the differential pressure (Δ

p) after the correction (reduction) is carried out.