Electric motor pump control incorporating pump element position information   

The invention relates to methods and systems for providing improved (or reduced) noise, vibration, and harshness (“NVH”) in the control of an electric motor of a hydraulic pump. More particularly, embodiments of the invention relate to method and a system for control of an electric motor driving a pump using information about the pump element position to control the power of the motor in order to reduce the NVH generated by the pump.

Generally, systems that include radial hydraulic pumps driven by an electric motor are known in the industry. Examples of these hydraulic systems include the Electronic Stability Program (“ESP®”) by Robert Bosch and more particularly the ESP® premium system, which is based on a conventional hydraulic braking system (although it can perform the functions of an electro-mechanical braking system). The ESP® premium system uses a hydraulic pump that has six pistons moved by an eccentric cam rotated by an electric motor. Other known hydraulic pumps systems include fewer pistons (two or three, for example).

A common characteristic for systems that include a hydraulic pump driven by an electric motor is that the pumping action generates pressure pulsations that create noise and vibration in the system. Depending on the number of pistons and the speed of the electric motor, the level of noise and vibrations varies from system to system.

SUMMARY

A variety of methods exist that help to reduce different types of NVH. For example, to help reduce vibration in an engine (e.g., V-twin motorcycle engine), a counterbalance effect method is applied. In order to minimize the engine\'s vibration, a mass is used to balance out the unevenly balanced engine and to bring the engine into equipoise (the weights or forces in the engine offset one another). Other methods for reducing noise are disclosed in, for example, noise-canceling headphones. However, the previously disclosed methods for reducing NVH do not propose reducing the noise and vibrations in a hydraulic pump by regulating the power of the electric motor of the pump based on the position of the pump element.

Thus, there is a need for an improved method and a system for controlling and reducing the NVH produced by a hydraulic pump system driven by an electric motor. Embodiments of the invention control and reduce the NVH of an electric motor of a hydraulic pump by using information about the pump element position relative to the pump stroke and manipulating or controlling the power of the electric motor based on the pump stroke position. Embodiments are applicable to both, brushed and brushless direct-current (“DC”) motors.

The invention provides a method for controlling an electric motor of a pump to counter act pressure pulsations generated by at least one pump element and to reduce noise, vibration, and harshness generated by the pump. The method determines a position of at least one pump element of the pump and a position of the shaft of the electric motor. Further, a pump stroke position is determined from the position of the pump element relative to the position of the shaft of the electric motor. The power sent to the electric motor is controlled according to the pump stroke position.

The invention also provides a system for controlling an electric motor of a pump to reduce noise, vibration, and harshness generated by least one pump element of the pump. The system includes a controller, and a plurality of sensors connected to the controller. Each of the sensors is configured to transmit information to the controller, and a network connects the sensors to the controller. The controller determines a position of a pump element and a position of a shaft of the electric motor. Further, the controller determines a pump stroke position from the position of the pump element relative to the position of the shaft of the electric motor. Finally, the controller controls a power sent to the electric motor according to the pump stroke position. Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an electric motor of a pump and components for controlling the electric motor using information about the pump element position.

FIG. 2 is a schematic illustration of a system for controlling an electric motor of a pump.

FIG. 3 is a block diagram of a pump electric motor control module.

FIG. 4 is a graph depicting a target power profile used by the system for controlling an electric motor of a pump shown in FIG. 1, where the target power is in phase with the pump element position.

FIG. 5 is a graph depicting a target power profile used by the system for controlling an electric motor of a pump shown in FIG. 1, where the target power is out of phase with the pump element position.

FIG. 6 is a graph depicting a target power profile used by the system for controlling an electric motor of a pump shown in FIG. 1, where the target power frequency is two times the pump element stroke.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.

As should be apparent to one of ordinary skill in the art, the systems shown in the figures are models of what actual systems might be like. It should also be noted that a plurality of hardware and software based devices, as well as a plurality of different structural components, may be utilized to implement the invention. Many of the modules and logical structures described are capable of being implemented in software executed by a microprocessor or a similar device or being implemented in hardware using a variety of components. As described in subsequent paragraphs, the specific configurations illustrated in the drawings are intended to exemplify embodiments of the invention and other alternative configurations are possible. Furthermore, throughout the specification capitalized terms are used. Such terms are used to conform to common practices and to help correlate the description with the coding examples, equations, and/or drawings. However, no specific meaning is implied or should be inferred simply due to the use of capitalization. Thus, the claims should not be limited to the specific examples or terminology provided.

FIG. 1 illustrates one embodiment of a system for control of an electric motor of a pump using information about the pump element position (e.g., a piston). The pump electric motor control system 12 generally includes a hydraulic pump 10 and position sensors 20 (not shown) that are located on or around a shaft 17 of the electric motor 18 of the pump 10. Further, the pump electric motor control system 12 includes a controller 24 (FIG. 2) and a power control device 25 (FIG. 3) that manipulates the power sent to the electric motor 18. In one of the embodiments, the system 12 uses several position sensors. However, as explained in greater detail below, the system 12 can also operate with one sensor 20 or without any sensors at all. In addition, the arrangement and the position of the sensors 20 of the system 12 can vary depending on the different embodiments of the system and the type of sensors used in those embodiments. Generally, the sensors 20 are directly connected to the controller 25. In an embodiment, the sensors are connected to a network, such as a controller area network (“CAN”) bus 22, which is connected to the controller 24.

As further show in FIG. 1, the hydraulic pump 10 includes an electric motor 18, an eccentric cam (or, simple “eccentric”) 14, a rotating shaft 17, and a number of pump elements (pistons) 16. The pump 10 is operatively connected to and driven by the motor 18. In one embodiment, the system 12 includes a pump 10 with three pump pistons 16. In alternative embodiments, the system 12 can include pumps with different number of pump pistons (two, four, six, etc.). The pump elements 16 are located near the motor 18 and are pushed up and down by the eccentric 14, which is rotated by the shaft 17 of the motor 18. Several position sensors 20 (not shown) are operatively coupled to the shaft 17 of the motor 18 and are connected to the controller 24.

In the embodiment shown in FIGS. 1-3, the system 12 determines the position of the pump element 16 (as a function of time) relative to the angular position of the shaft 17 (i.e., relative to the pump stroke) in order to control the power sent to the electric motor 18. The rotation of the shaft 17 of the electric motor 18 has a fixed relationship to the movement of the pump element 16. Thus, by controlling the power of the electric motor 18 in relation to this pump stroke position, the system 12 affects (i.e. reduces) the noise and vibration levels created by the pump 10. In other words, the system 12 determines whether the pump element 16 is pumping fluid or not in a particular moment so it can pulse the motor power or otherwise control it based on the pump element position.

As described in greater detail below, the position of the pump element 16 and the shaft 17 can be determined directly by using a position sensor or a plurality of position sensors, or indirectly by monitoring and measuring the motor voltage. After the position of the pump element is determined, the system selects a “target power profile” from a table with various target power profiles stored in the memory of the controller in order to regulate the power sent to the motor 18. This target power is based on the previously determined pump element position. The system 12 uses a power control device 25 (an amplifier, a transducer, or another type of transformation device) to manipulate the electrical energy sent to the pump motor 18 to affect (i.e., counter act) the pressure pulsations generated by the stroke of the reciprocating pump element 16.

In one embodiment of the invention, the system 12 obtains information about the position of the pump element directly by using several position sensors. These position sensors 20 are placed on or around the shaft 17 of the electric motor 18. The controller 24 receives the appropriate sensor signals and inputs from the position sensors 20 that indicate the position of the pump elements 16 and the angular position of the shaft 17. For example, direct position measurement could be accomplished by using Hall effect sensors or rotary encoders. Other position sensors can also be used.

One embodiment of the invention utilizes an advanced (and more expensive) sensor array having a large number of position sensors (Hall effect sensors), which are positioned on or around the rotating shaft 17. By using an advanced sensor array, the system 12 obtains more precise position information of the pump element and the shaft.

In an alternative embodiment, where the system 12 is built inexpensively, only a single position sensor is used to determine the pump stroke position. In that case, the system receives position information for only part of the rotation of the shaft 17 (for example the system can receive a pulse for 5 degrees on every rotation). The system 12 then estimates the position of the shaft 17 for the rest of the rotation based on various additional factors—the rpm of the electric motor, the sum of torques acting on the motor, and the overall pressure that the pump 10 is working against. The system combines these factors with the initial sensor measurement in order to estimate the future position of the pump element and subsequently verifies whether this position is correct.

In another alternative embodiment, the system 12 uses electrical monitoring to indirectly determine the position of the pump element 16 in relation to the pump stroke. In this alternative embodiment, the system 12 determines the position of the pump elements 16 and the shaft 17 without any position sensors 20. For example, in a brushed DC motor, the system 12 measures the electrical signal of the motor wire as the communicator switches from one winding to another in order to determine the position of the shaft 17 and the pump element 16. A similar method for indirectly determining the position of the electric motor and the pump element is described in EP 2096749 A1. The system 12 can also indirectly determine the position of the electric motor and the pump elements in a brushless DC motor. Thus, the position of the pump element 16 and the shaft 17 can be also determined indirectly without the use of position sensors. Although it is possible to implement, indirect or “sensorless” determination of the pump element position is not preferred for electronic stability control systems because the electric motor starts and stops frequently and the starting and stopping makes it difficult to keep track of the position of the motor elements.

FIG. 2 schematically illustrates the functionality of the pump electric motor control system 12 of FIG. 1 in greater detail. As shown in FIG. 2, the control system 12 includes the controller 24 and one or more sensors 20. The controller 24 obtains sensor readings directly from one or more of the sensors 20. In some circumstances, especially when the system uses less sensors to determine the position of the pump element 16, compensated sensor readings are used by the controller 24, rather than raw data. For example, in some circumstances, the controller 24 compensates one or more of the sensor readings by applying an offset. Offsets are used to compensate for sensor aging, fouling, and other signal corruption that may occur.

In many implementations, controller 24 includes a processor such as a microcontroller or microprocessor, associated electronic circuitry such as input/output circuitry, various programmed modules, and one or more memory components.

As shown in FIG. 2, the controller 24 includes an input/output interface 40, an electronic processing unit (“EPU”) 42, and one or more memory modules, such as a random access memory (“RAM”) 44 and read-only memory (“ROM”) 45. The input/output interface 40 transmits and/or receives information, including sensor readings from the sensors 20. The controller 24 also includes a pump electric motor control (“PEMC”) module 50 that is executed by the EPU 42. The PEMC module 50 is architected to determine the position of the shaft 17 and the pump element 16 relative to the pump stroke and controls the power of the electric motor 18 in relation to the determined control position.

The EPU 42 receives information (such as sensor readings) from the input/output interface 40 and processes the information by executing one or more applications or modules. The applications or modules are stored in memory, such as ROM 45. The EPU 42 stores information (e.g., information received from the sensors 20, or information generated by applications or modules executed by the EPU 42) to the RAM 44. For example, the RAM 44 can store the various positions of the shaft 17 and the pump elements 16 that are detected by the sensor 20. In addition, the RAM 44 can also receive and store data from the PEMC module 50 or other components of the system 12. The RAM 44 also stores a table with various target power profiles that is accessed by the PEMC module 50 in order to select a target control power that manipulates the electric motor 18. In the embodiment shown in FIG. 2, RAM is used. In other embodiments, other memory devices can be also implemented.

FIG. 3 illustrates the operation of pump electric motor control (“PEMC”) module 50 in greater detail. In the particular embodiment illustrated, the PEMC module 50 is configured to determine the position (stroke) of the pump element 16, which has a set relationship with the electric motor 18 as the motor shaft 17 rotates, and to control the power of the electric motor 18 in relation to the pump stroke position. The PEMC module 50 receives sensor signals from the sensors 20 (or in the alternative embodiment a single sensor) through the input/output interface 40 and based on these signals determines the position of the pump element 16. The PEMC module 50 determines the pump stroke position—this is the position of the pump element 16 relative to the pump stroke (i.e., the motion of the pump element as the pump is moving or whether the pump element is pumping fluid or not). The pump stroke position is determined based on the position of the electric motor 18 (using the motor shaft position) relative to the position of the pump element 16. The PEMC module 50 then selects a target control power from the table with target power profiles according to the determined pump stroke position.

The PEMC module 50 uses the power control device 25 to manipulate the power sent to the electric motor 18 in accordance with the selected target control power. Controlling the power sent to the motor 18 includes voltage control (e.g., pulse width modulation control) or current control (e.g., by specific hardware) depending on the implementation of the system. By regulating the power of the electric motor 18 in relation to the stroke of the pump element 16, the PEMC module 50 helps to affect (i.e. reduce) noise, vibration, and harshness generated by the pump 10. In one embodiment, the power control device 25 is a metal-oxide-semiconductor, field-effect transistor (MOSFET) control device. In alternative embodiments, the power control device 25 can be an amplifier, transducer, or other control device.

In order to timely change the power of the motor 18 based on the position of the pump element 16, the system 12 executes the PEMC module 50 at a high rate in order to keep up with the repeating pressure pulse created by the pump elements 16. For example, in a pump with two pump elements, the motor 18 operates at 5000 rpm (equal to 83.3 Hz) and produces 167 pulses per second (5000 rpm times two). The system 12 executes the PEMC module 50 approximately 10 times faster than an individual pump element cycle. Thus, in this case, the PEMC module 50 is executed for approximately every (1 sec/167 pulses)*(0.1)=0.6 ms. During the PEMC module execution time (0.6 ms=0.0006 s), the system 12 determines the pump stroke position, selects a target control power from the table with target power profiles, and regulates the voltage of the motor 18.

The operation of the pump electric motor control (“PEMC”) module 50 is further illustrated in FIGS. 4-6. In particular, FIGS. 4-6 represent several target power profiles that are stored in the RAM 44 and are used by the PEMC module 50 in order to select a target control power to control the electric motor 18. Additional target power profiles can be created and used in various embodiments of the invention. The waveform graphs in FIGS. 4-6 represent embodiments of the invention where the pump 10 includes three pump elements or pistons 16 (as shown in FIG. 1). In alternative embodiments of the invention, a different number of pump elements can be used. The waves at the lower portion of FIGS. 4-6 represent the movement/stroke of the pump elements 16. In general, these pump elements 16 generate a pressure pulse every 120 degrees. The measurements on the left hand side of the graphs represent the pump element position relative to the pump stroke (in mm). The measurements on the right hand side of the graphs represent the level of the target control power (in amperes). The measurements on the bottom of the graph represent the angular position of the shaft 17 (in degrees). The target control power illustrated in the upper portion of the graph is a function of the shaft position in relation to the pump element position. For example, if the pump element is at 240 degrees position the target power is 8.5 amperes.

FIG. 4 represents one target power profile that is used by the system 12. After the system 12 determines the pump stroke position based on the pump element position and the shaft angular position, the system 12 selects a target power profile from the table stored in RAM 44. FIG. 4 shows a situation where the target power is in phase with the pump element position. In other words, the target power will increase when the pump is moving and will decrease when the pump is not. Thus, system 12 provides most power to the electric motor 18 when the pump is doing most of the work.

FIG. 5 illustrates a second target power profile that is used by the system 12. In FIG. 5, the target power is out of phase with the pump element position. In other words, the target power will be less when the pump element is moving and the target power will go up when the pump is not moving. Thus, the target power creates an oscillation wave that is exactly out of phase with the pump noise wave and the two waves will interact. In the right condition, these two opposite phase oscillations can combine with the result being a smaller wave.

FIG. 6 shows a third target power profile that is used by the system 12. The target power profile illustrated in FIG. 6 shows that when the system 12 determines the pump element position, the system 12 can adjust the target power (at an increased or decreased level) in order to obtain the best overall performance of the pump 10. In this case, the target power is two times the pump element stroke and is in phase with the pump element position. The system manipulates the target power with respect to the pump stroke in such a manner in order to improve NVH of the pump.

Various features and advantages of the invention are set forth in the following claims.