Current monitoring in a load

Abstract

A method for determining a current that flows through a load, wherein the current comprises a DC component and a dithering component, and the dithering component is modified in predetermined time intervals, comprises steps for recording a momentary current; determining a dithering parameter; and determining the current based on the momentary current and the dithering parameter.

Claims

1. A method for determining an average value of a current that flows through a load, wherein the current comprises a DC component and a dithering component, and the dithering component is periodically modified in predetermined time intervals in a predetermined curve shape, the method comprising: recording a momentary current; determining dithering parameters of a period length, an amplitude, and a curve shape of the dithering component; and determining the average value of the current based on the momentary current and the dithering parameters.

2. An activation device for activating a current through a load, wherein the current comprises a predetermined direct current and a dithering current periodically modified in predetermined time intervals on a basis of dithering parameters, wherein the dithering parameters comprise a period length, an amplitude, and a curve shape of the dithering component, the activation device comprising: a sampling device for determining a momentary current through the load and an interface for supplying the momentary current and the dithering parameters.

3. A device for determining an average value of a current through a load, which is activated by means of an activation device such that the current comprises a predetermined direct current and a dithering current periodically modified in predetermined time intervals on a basis of dithering parameters, wherein the dithering parameters comprise a period length, an amplitude, and a curve shape of the dithering component, the device configured to: request a momentary current determined by the activation device; and determine the average value of the current through the load based on the momentary current and the dithering parameters.

4. A method for determining an effective value of a current that flows through a load, wherein the current comprises a DC component and a dithering component, and the dithering component is periodically modified in predetermined time intervals in a predetermined curve shape, the method comprising: recording a momentary current; determining dithering parameters of a period length, an amplitude, and a curve shape of the dithering component; and determining the effective value of the current over a period, based on the momentary current and the dithering parameters.

5. A method for determining a DC component of a current that flows through a load, wherein the current comprises a DC component and a dithering component, and the dithering component is modified in predetermined time intervals, the method comprising: recording a momentary current; determining the value of the dithering component; and determining the current based on the momentary current and the value of the dithering component.

6. A device for determining an average value of a current through a load, which is activated by an activation device such that the current comprises a predetermined direct current and dithering current periodically modified in predetermined time intervals on the basis of dithering parameters, wherein the dithering parameters comprise a period length, an amplitude, and a curve shape of the dithering component, the device configured to: request a momentary current determined by means of the activation device and the dithering parameters; and determine the average value of the current through the load based on the momentary current and the dithering parameters.

7. A device for determining a DC component of a current through a load, which is activated by an activation device such that the current comprises a predetermined direct current component and a dithering component modified in predetermined time intervals, the device configured to: request a momentary current determined by the activation device and a value of the dithering component; and determine the DC component of the current through the load based on the momentary current and the dithering component.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention shall now be described in greater detail with reference to the attached figures, in which:

(2) FIG. 1 shows a circuit diagram for a system for controlling a current through a load;

(3) FIG. 2 shows an exemplary curve for a current through the load shown in FIG. 1; and

(4) FIG. 3 shows a flow chart for a method for determining the current flowing through the load shown in FIG. 1.

DETAILED DESCRIPTION

(5) FIG. 1 shows a circuit diagram for a system 100 for controlling a current through a load 105. The load 105 can comprise, in particular, a continuous current-controlled hydraulic valve, in particular a continuous valve. The continuous valve allows for a continuous transition between switch positions, such that a volume flow of a hydraulic fluid can be adjusted proportionally. The continuous valve can comprise a proportional valve, a regulating valve, or a servo valve, in particular for controlling a gearing in a drive train of a motor vehicle, for example. In the depicted embodiment, the load 105 thus comprises a coil 110 with an armature 115, also referred to as a solenoid armature, that acts on a hydraulic piston 120, also referred to as a control piston. A hydraulic circuit through the hydraulic valve is not shown in FIG. 1.

(6) A current through the load 105 is supplied by a current source 125, and controlled by means of an activation device 130. The activation device 130 can communicate with a control device 135 by means of an interface 140. The control device 135 normally comprises a processor 145, which is configured to determine a specification for the current flowing through the load 105, and to send this to the activation device 130, in order to fulfill a predetermined control task.

(7) The activation device 130 comprises a processor 150, a current control 155 for controlling a current flowing through the load 105, and a sampling device 160 for determining a momentary value of the current flowing through the load 105. In the illustrated embodiment, a series resistor (shunt) is inserted in the current path of the load 105, wherein the sampling device 160 determines a voltage passing through the series resistor 165.

(8) The current control 155 is configured to adjust a current through the load 105 composed of two components. A DC component can preferably be specified externally via the interface 140, and dithering component is generated by the current control 155. The dithering component shall be described in greater detail below in reference to FIG. 2. Parameters for executing the dithering can be stored permanently in the activation device 130, or can be entered externally by means of the interface 140. The dithering parameters are normally initialized only once, and then no longer modified. The DC component that is to flow through the load 105 is then entered externally via the interface 140 as needed, and implemented automatically by the activation device 130 or the current control 155. If the current actually flowing through the load 105 is to be supplied, then the momentary current can be sampled by means of the sampling device 160.

(9) It is proposed that the sampled momentary current be calculated on the basis of a dithering parameter that applies at the time of the sampling, in order to determine the current through the load 105 as an average value, effective value, or in the form of a DC component. In a first variation, the momentary current and the dithering parameter can be processed by the activation device 130, such that the determined current can be exported by means of the interface, and in another variation, the momentary current and the dithering parameters are exported via the interface 140, and a determination of the current takes place externally, e.g. by means of the control device 135, or its processor 145.

(10) FIG. 2 shows an exemplary curve of a current 205 through the load 105. The current 205 is composed at all times of a DC component 210 and a dithering component 215. The dithering component 215 can be only positive, only negative, or, as depicted, positive or negative at different points in time, in relation to the DC component 210. The dithering component 215 changes at predetermined time intervals 220, wherein a predetermined number of time intervals 220 results in a period length 225. Further parameters affecting the dithering can comprise an amplitude 230 or an increment 235. Furthermore, a curve shape of the dithering component 215 is decisive for the absolute value thereof at an arbitrary point in time.

(11) A triangular dithering is shown by way of example, which is frequently used for controlling a hydraulic valve serving as the load 105. The dithering component 215 increases at constant increments 235 in the time intervals 220 0 to k to a maximum amplitude 230, is then reduced in increments until reaching a time interval 220 3k, and is then again increased in increments until reaching the time interval 220 4k1. The decreasing and increasing take place in a linear manner over time. The variable k can be specified in order to produce a predefined relationship between the period length 225 of the dithering and the time interval 220.

(12) The average of the dithering component 215 over a complete period 225 is 0 in the depicted triangular shape. The effective value of the dithering component 215 corresponds to 2/{square root over (3)} of the peak value in the selected triangular form, wherein the peak value is the difference between the maximum value and the minimum value of the dithering component 215, thus corresponding to twice the amplitude 230 in this case. Other curve shapes than the triangular shape are also possible, e.g. a sine wave, sawtooth, or rectangular curve form can be used in other embodiments.

(13) The activation device 130 is configured to superimpose the dithering component 215 with the externally specified DC component 210. The dithering component 215 is determined entirely by the activation device 130 thereby, on the basis of the specified parameters 220 to 235, the shape of the curve, and other applicable parameters.

(14) In order to determine the current 205 flowing through the load 105 at a specific point in time, an average value or effective value of the current 205 can be determined over a period 225 with different embodiments of the DC component 210. The determination takes place thereby on the basis of a momentary current flowing through the load 105, and one or more dithering parameters. The momentary current is a current value that flows through the load 105 within a time interval 220 at which the determination is carried out.

(15) FIG. 3 shows a flow chart for a method 300 for determining the current 205 flowing through the load 105 shown in FIG. 1. Steps shown in the left-hand region are preferably carried out by the control device 135, whereas steps shown in the right-hand region are preferably processed by the activation device 130.

(16) Independently of the actual determination of the current, a dithering parameter is normally determined by the control device 135 in step 305, and assumed or activated by the activation device 130 in step 310. Depending on the configuration of the interface 140, the communication between the control device 135 and the activation device 130 can comprise an addressing and access to one or more predefined registers by one of the components 130, 135. Each dithering parameter can have its own register in the activation device 130. The control device 135 can then write appropriate values for the desired dithering parameters in the individual registers.

(17) In a normal operation of the system 100, a desired DC component 210 is determined in step 315, sent to the activation device 130, and assumed or activated there in step 320. Steps 315 and 320 are normally executed repeatedly.

(18) In order for the control device 135 to determine the current through the load 105, a current determination is requested in step 325, and executed by the activation device 130 in step 330. The determined momentary current and at least one dithering parameter are provided or supplied in step 335, and a determination of the actual current flowing through the load 105 by the control device 135 is established in step 340. The dithering parameter in step 335, and potentially other parameters, are used thereby, which are known, for example, by the control device 135 from one of the steps 305 or 315. The other parameters can comprise, for example, a period length for the dithering, or a dithering frequency (step 305).

(19) The determination of the current 205 can also be carried out in another embodiment by the activation device 130. The determined current is subsequently sent or supplied to the control device 135.

(20) In order to determine the current 205 on the basis of the momentary current, normally at least the time interval 220 in which the dithering took place when the momentary current was determined must be known. The dithering component 215 can then be computed as an absolute value, e.g. when the curve shape, and the period length 225, or the variable k in the example shown in FIG. 2 are known. The desired current 205 can then be determined based on the momentary current minus the dithering component 215.

(21) It is preferred that only one dithering parameter, based on an individual current determination, is exported together with the momentary current by the activation device 130. In particular, the dithering parameter can also be provided as a numerical index, indicating the time interval 220 in which the momentary current is determined. The index is preferably reset to a predetermined value by the activation device 130 after each period 225, and incremented successively at each time interval 220. If the interface is an SPI bus, one or more registers can be provided for the momentary current, and one or more registers can be provided for the index.

REFERENCE SYMBOLS

(22) 100 system 105 load 110 coil 115 armature 120 piston 125 current source 130 activation device 135 control device 140 interface 145 processor 150 processor 155 current control 160 sampling device 165 series resistor 205 current 210 DC component 215 dithering component 220 time interval 225 period length 230 amplitude 235 increment 300 method 305 dithering parameter determination 310 dithering parameter assumption/activation 315 DC component determination 320 DC component assumption/activation 325 current determination request 330 current determination execution 335 sending of determined momentary current and at least one dithering parameter 340 current determination