Method for determining a control force of an actuator

Abstract

A method for determining an operating force (F.sub.p) of a positioning actuator (3), whose adjustment movements are produced by virtue of an appropriate supply of a working medium via actuating at least one valve (4 to 7) associated with the positioning actuator (3). The operating force (F.sub.p) is determined by computational determination. To be able to carry out the computational determination of the operating force (F.sub.p) with little effort, by the at least one valve (4 to 7) in each case, a respective, essentially constant mass flow ({dot over (m)}.sub.iv, {dot over (m)}.sub.ov) of working medium is maintained either into the positioning actuator (3) and/or out of the positioning actuator (3).

Claims

1. A method of determining an operating force (F.sub.p) of a positioning actuator (3), whose adjustment movement is produced by a supply of a working medium by actuation of first and second valves which communicates with the positioning actuator (3), the method comprising: producing an essentially constant mass flow ({dot over (m)}.sub.iv, {dot over (m)}.sub.ov) of the working medium by the first and the second valves either: into the positioning actuator (3), or out of the positioning actuator (3) thus reducing an influence of non-linear factors; on the operating force determining the operating force (F.sub.p) using computation performed, via a control unit, during operation of a motor vehicle clutch; creating a characteristic curve using a polynomial; and comparing the operating force (F.sub.p) to the characteristic curve, via the control unit, to determine a wear condition the motor vehicle clutch.

2. The method according to claim 1, further comprising actuating the motor vehicle clutch (1) using the positioning actuator (3) in such manner that the operating force (F.sub.p) of the positioning actuator (3) represents a release force of the motor vehicle clutch (1).

3. The method according to claim 2, further comprising creating the characteristic curve of the release force by varying the operating force (F.sub.p(t)) and taking into account respective clutch positions (z(t)) of the motor vehicle clutch (1).

4. The method according to claim 3, further comprising, after creation of the characteristic curve of the release force, determining, via the control unit, parameters for regulation of the motor vehicle clutch (1) by a gain-scheduling method.

5. The method according to claim 2, further comprising keeping an incoming mass flow ({dot over (m)}.sub.iv) essentially constant via the first valve (4, 5).

6. The method according to claim 2, further comprising keeping an outgoing mass flow ({dot over (m)}.sub.ov) essentially constant via the second valve (6, 7).

7. The method according to claim 1, further comprising controlling the first and the second valves with a low frequency, in a range 5 to 20 Hz, to set the essentially constant incoming mass flow ({dot over (m)}.sub.iv) and the essentially constant outgoing mass flow ({dot over (m)}.sub.ov).

8. An actuating mechanism (2) for a motor vehicle clutch (1) comprising a positioning actuator (3) whose adjustment movement is produced by a supply of compressed air by actuation of first and second valves that communicates with the positioning actuator (3), and an operating force (Fp) of the positioning actuator (3) being determined by a method comprising: producing an essentially constant mass flow ({dot over (m)}.sub.iv, {dot over (m)}.sub.ov)of the compressed air by the first and second valves either: into the positioning actuator (3), or out of the positioning actuator (3) thus reducing an influence of non-linear factors; on the operating force determining the operating force (F.sub.p)using computation performed, via a control unit, during operation of the motor vehicle clutch; creating a characteristic curve using a polynomial and comparing the operating force (F.sub.p) to the characteristic curve, via the control unit, to determine a wear condition the motor vehicle clutch.

9. The actuating mechanism (2) according to claim 8, further comprising a computer program product for determining the actuating force (Fp) of the positioning actuator (3), the computer program product issuing corresponding commands, stored in a software module on the control unit, for setting the respective essentially constant mass flow ({dot over (m)}.sub.iv, {dot over (m)}.sub.ov) of the compressed air into the positioning actuator (3) and out of the positioning actuator (3), and determining the operating force (Fp) of the positioning actuator (3) using the following formula for disengaging the vehicle clutch: $\begin{array}{c}{F}_p\left(t\right)=\frac{\left(m_0+\stackrel{.}{m}.Math.t\right).Math.R.Math.T}{\frac{V_0}{A}+l_{max}-z\left(t\right)}\\ \mathrm{and}\\ F_p\left(t\right)=\frac{(m_{max}+\stackrel{.}{m}+T_s.Math.\left(p_z/p_s\right).Math.R.Math.T}{\frac{V_0}{A}+l_{max}-z\left(t\right)}\end{array}$ for engaging vehicle clutch, where m.sub.o is an air mass of a dead volume of the positioning actuator, {dot over (m)} is respective constant mass flow, R is a specific gas constant, T is a specific gas temperature, V.sub.ois the dead volume, A is a piston area of a piston of the positioning actuator, p.sub.z is an internal pressure of a cylinder, p.sub.s is a reservoir pressure of a reservoir that supplies the positioning actuator, and m.sub.max is an air mass in the positioning actuator when the piston is fully extended.

10. The actuating mechanism (2) according to claim 9, further comprising a data carrier upon which the computer program product is stored.

11. The actuating mechanism according to claim 8, further comprising actuating the motor vehicle clutch (1) using the positioning actuator (3) in such manner that the operating force (F.sub.p) of the positioning actuator (3) represents a release force of the motor vehicle clutch (1).

12. The actuating mechanism according to claim 11, further comprising creating the characteristic curve of the release force by varying the operating force (F.sub.p(t)) and taking into account respective clutch positions (z(t)) of the motor vehicle dutch (1).

13. The actuating mechanism according to claim 12, further comprising, after creation of the characteristic curve of the release force, determining, via the control unit, parameters for regulation of the motor vehicle clutch (1) by a gain-scheduling method.

14. The actuating mechanism according to claim 11, further comprising keeping an incoming mass flow ({dot over (m)}.sub.iv) essentially constant via the first valve (4, 5).

15. The actuating mechanism according to claim 11, further comprising keeping an outgoing mass flow ({dot over (m)}.sub.ov) essentially constant via the second valve (6, 7).

16. The actuating mechanism according to claim 8, further comprising controlling the first and second valves with a low frequency in a range 5 to 20 Hz to set the essentially constant mass flow ({dot over (m)}.sub.iv, {dot over (m)}.sub.ov).

17. A data carrier for storing a computer program product for an actuating mechanism (2) having a positioning actuator (3) for a motor vehicle clutch (1), the positioning actuator (3) being movable by a supply of a working medium by actuation of first and second valves that communicates with the positioning actuator (3), and an operating force (Fp) of the positioning actuator (3) being determined by a method comprising: producing an essentially constant mass flow ({dot over (m)}.sub.iv, {dot over (m)}.sub.ov) of the working medium by the first and second valves either: into the positioning actuator (3), or out of the positioning actuator (3) thus reducing an influence of non-linear factors; on the operating force determining the operating force (F.sub.p) using computation performed on a control unit during operation of the motor vehicle clutch; creating characteristic curve using a polynomial; and comparing the operating force(F.sub.p) to the characteristic curve, via the control unit, to determine a wear condition the motor vehicle clutch, the computer program carrying out corresponding commands, that are stored in a software module in the control unit, for setting in each case of the essentially constant mass flow ({dot over (m)}.sub.iv, {dot over (m)}.sub.ov) of the working medium at least one of into the positioning actuator (3) and out of the positioning actuator (3).

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) An advantageous design of the invention, which will be described below, is represented in the drawing. The sole FIGURE shows a schematic illustration of a clutch mechanism of a motor vehicle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(2) The motor vehicle comprises a vehicle clutch 1 in the form of a separator clutch and an operating mechanism 2 associated with the motor vehicle clutch 1. In this case the motor vehicle clutch 1 is of a type whose principle is well known to anyone with knowledge of the field, and need not therefore be described further here.

(3) As can be seen from the single FIGURE, the operating mechanism 2 comprises essentially a positioning actuator 3 and valves 4 to 7. Furthermore, in this case the positioning actuator 3 is in the form of a piston-cylinder unit wherein a piston 9 can move axially inside a hollow cylinder 8. When an inside space 10 of the positioning actuator 3 is filled with a working medium in the form of compressed air, the piston 9 undergoes an adjustment movement in the direction toward the motor vehicle clutch 1 and thereby opens the clutch in opposition to spring elements (not shown in more detail here). A movement of the piston 9 within the hollow cylinder 8 is limited toward the bottom 11 of the hollow cylinder 8 by a mechanical stop 12, which thus also defines a maximum travel path I.sub.max of the positioning actuator 3,

(4) The supply of compressed air to the inside space 10 is, in this case, controlled by the valves 4 and 5, which are, in each case, designed as directional valves with discrete switching positions, but which have through-flow cross-sections different from one another. When compressed air is passed into the inside space 10 by way of the valves 4 and 5, the motor vehicle clutch 1 is acted upon by an actuating force F.sub.p determined by the input mass flow {dot over (m)}.sub.iv supplied. If the motor vehicle clutch 1 is then to be closed, the compressed air is allowed to escape from the inside space 10 by way of the valves 6 and 7, which are also designed as directional valves with discrete switching positions but through-flow cross-sections different from one another. A defined mass flow {dot over (m)}.sub.ov determined by the valves 6 and 7 defines the characteristic for the closing of the motor vehicle clutch 1.

(5) Depending on the position of the piston 9 in the hollow cylinder 8, different clutch positions z are also defined, such that one position of the piston 9 corresponds to a contact point z.sub.cp beyond which, during the course of its closure, the motor vehicle clutch 1 can for the first time transmit torque, i.e. the two halves of the clutch come in contact with one another for the first time,

(6) In order, now, to be able to determine the release force F.sub.p of the motor vehicle clutch 1 by computation in a simple manner during operation, according to the invention an actuation frequency of the valves 4 to 7 is chosen in a range from 5 to 20 Hz, preferably 10 Hz, whereupon the two mass flows {dot over (m)}.sub.iv and {dot over (m)}.sub.ov are essentially constant. Consequently, the release force F.sub.p for opening can be calculated in accordance with the formula:

(7) $F_p\left(t\right)=\frac{\left(m_0+\stackrel{.}{m}.Math.t\right).Math.R.Math.T}{\frac{V_0}{A}+l_{\mathrm{ma}x}-z\left(t\right)}$
and for closing by the formula:

(8) $F_p\left(t\right)=\frac{(m_{\mathrm{ma}x}+\stackrel{.}{m}.Math.T_s.Math.\left(p_z\text{/}{p}_s\right).Math.R.Math.T}{\frac{V_0}{A}+l_{\mathrm{ma}x}-z\left(t\right)}$
in which m.sub.0 is the air mass of the dead volume of the positioning actuator, {dot over (m)} is the respective constant mass flow, R is the specific gas constant, 1 is the specific gas temperature, V.sub.0 is the dead volume, A is the piston area of the piston 9, p.sub.z is the internal pressure of the cylinder, p.sub.s is the reservoir pressure of a reservoir that supplies the positioning actuator, and m.sub.max is the air mass in the positioning actuator when the piston is fully extended.

(9) Thereafter, from the respective release forces F.sub.p(t) and the associated clutch positions z.sub.(t), by means of a suitable polynomial, a characteristic curve of the release force is determined and stored in an EEPROM of the clutch control unit or the transmission control unit. The routine for determining the polynomial coefficients is preferably initiated with the motor vehicle at rest and with a gear engaged by locating the contact point z.sub.cp, although it can also be initiated in the context of a diagnosis demand.

(10) Thereafter, with the help of a gain-scheduling method, adaptation of control parameters of the positioning actuator 3 to the characteristic determined is carried out, in order to be able to regulate the opening and closing of the motor vehicle clutch 1 under conditions that may have changed in the meantime.

(11) By virtue of a method according to the invention for determining an operating force of a positioning actuator, the operating force can be determined by computational means with little cost and effort.

INDEXES

(12) 1 Motor vehicle cutch 2 Actuating mechanism 3 Positioning actuator 4 Valve 5 Valve 6 Valve 7 Valve 8 Hollow cylinder 9 Piston 10 inside space 11 Bottom 12 Stop I.sub.max Maximum travel path {dot over (m)}.sub.iv Incoming mass flow {dot over (m)}.sub.ov Outgoing mass flow F.sub.p Actuation force z Clutch position z.sub.cp Contact point