System for calibrating starting current of an electro-hydraulic pump based on engine output torque signal

Abstract

A system for calibrating an electro-hydraulic pump is for a vehicle having a propulsion system that includes an engine connected to the electro-hydraulic pump. A microcontroller having software and an input device is connected to a plurality of sensors mounted around the vehicle. The software uses a plurality of parameters to convert an internal analog drive signal into an analog output signal for controlling the electro-hydraulic pump and the movement of a machine, wherein the parameters include a forward starting current value and a reverse starting current value.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 272,996, filed on October 28, 2021, the content of which is incorporated herein by reference in its entirety. Background Art

[0003] The present invention relates to the calibration of electro - hydraulic propulsion systems. More specifically, the present invention relates to the calibration of starting current parameters of an electro - hydraulic pump, including both forward starting current values and reverse starting current values for each pump.

[0004] Due to design tolerances and other variations in the manufacture of hydrostatic components, such as variable - displacement, axial - piston pumps, it is often necessary to "calibrate" each component at the end of assembly and / or after building each component into a complete system on a vehicle. Calibration procedures typically focus on identifying values of control inputs associated with different operating conditions of the pump or the entire system. For example, calibration establishes the relationship between the control input to the pump and its resulting behavior under different conditions.

[0005] It is generally recognized in the industry that calibration of pumps and motors on each vehicle is necessary to optimize the performance of advanced electro - hydraulic propulsion systems and maintain consistent performance from vehicle to vehicle. Pump starting current is a particularly important parameter because it is used to stroke the pump and move the vehicle when the drive pedal or other input device is controlled. In practice, the starting current of a pump can vary significantly but still be considered "within specifications". Incorrect parameter values of the starting current can cause the vehicle to jump into motion, result in a large dead zone or delay between pressing the drive pedal and the start of vehicle movement, or lead to a perceived lack of overall vehicle controllability.

[0006] In recent years, the market has increasingly focused on simplifying and improving the process of calibrating and configuring vehicles. Generally, there is a desire for a robust pump calibration procedure that runs automatically and does not rely on the presence of additional sensors or direct interaction with a skilled technician.

[0007] There are multiple ways to perform starting current calibration, and currently there are four commonly used methods. One system uses a pressure sensor to provide feedback to the controller to indicate the level of pressure when controlling the current generation threshold level when the pump enters the stroke under blocked port or locked motor conditions. The main drawback of this system is that most vehicles in this market do not have a system pressure sensor installed as factory equipment due to increased cost and complexity. These machine markets are highly competitive and price-sensitive, and even relatively inexpensive pressure sensors will be omitted if their functionality cannot be fully justified. Some vehicle OEMs will install a temporary system pressure sensor at the end of their assembly process in order to perform high-quality system calibration. This step increases the time and complexity of the assembly process and even increases the risk of introducing contaminants into the circuit when adding and removing the pressure sensor. This method also requires the vehicle service center to use specific equipment in the case of repairs or component replacements during the vehicle's life.

[0008] Another method uses a type of "drive" calibration where the vehicle is driven on a test track or the wheels are in the air. This procedure slowly increases the control current until the motor is detected to be moving, and then saves that value as the starting current. The main drawback of this method is that it requires access to a suitable test area and test operator, or it requires the vehicle to be jacked up in the air before performing the method. Additionally, the drawback is that the accuracy of this method may depend on the rolling resistance at the test location.

[0009] Another method uses a test operator or technician with sufficient skill to manually adjust the starting current parameters on the vehicle and observe the effect on the vehicle. This is an iterative process of making changes and then testing the performance until the results meet their expectations. The main drawback of this method is that it requires a test area and a skilled technician who can determine when the vehicle has reached an appropriate performance level. Otherwise, the quality of the results may vary. Also, the process is iterative and somewhat slow.

[0010] A new method developed in recent years involves the pump manufacturer performing specific tests on each pump at its factory, saving the results in a database, and then providing specific pump parameter data to the machine OEM after the pump is assembled into the machine. This method relies on identifying each pump by its serial number and accessing the parameters (e.g., starting current) from a cloud server or other database. The main drawback of this method is that it requires an IT system to be installed at the vehicle OEM in order to be able to quickly identify the pump serial number and obtain the parameters from the online database. This can be expensive and troublesome for many OEMs. Additionally, this method is only useful during the initial machine startup and is useless during the service life of the vehicle or in the case of repairs.

[0011] To overcome these drawbacks, it is desirable to use the load signal that exists on almost all modern vehicles with electronically controlled engines instead of an additional sensor. Another desire is to use a stationary procedure with the wheels on the ground, which may be part of the end-of-line testing at the vehicle factory. Another desire is to use a procedure that can automatically run and produce results based on intelligent software logic without manual adjustment or operator judgment. Yet another desire is to have a procedure that can be rerun at any time during the life of the vehicle without the need for specific equipment or skilled technicians. This means that after a service or other repair, the vehicle can be easily recalibrated, and even in the case of component wear, the vehicle performance can be maintained at a high level. The final desire is a procedure that eliminates the need for a specific calibration procedure (which may increase the overall assembly time) during pump assembly.

[0012] These and other objects, features, and advantages of the present invention will become apparent from the specification and claims. Summary of the Invention

[0013] A system for calibrating an electro-hydraulic pump includes a vehicle having a propulsion system that includes an engine connected to the electro-hydraulic pump. A microcontroller having software and an input device is connected to a plurality of sensors mounted around the vehicle. The software uses a plurality of parameters to convert an internal analog drive signal into an analog output signal to control the movement of the electro-hydraulic pump and the machine, wherein the parameters include a forward starting current value and a reverse starting current value.

[0014] In one example, the sensor is a load sensor, and the electro-hydraulic pump is a feedback-free electro-controlled pump. When the input device is controlled by an operator, the starting current value causes the electro-hydraulic pump to enter a stroke, and the calibration process is started by using a button on a service tool. The software commands the hydraulic motor to reach a displacement between 0% and 25%, and in one example, between 20% and 25%. The flow is pumped into the dead volume and is not consumed by the working device.

[0015] To determine the baseline engine load, the software commands the engine to reach a constant speed and does not command the electro-hydraulic pump. The software also ramps up the electro-hydraulic pump at a configurable rate to determine a configurable minimum value. The software determines and stores the starting current by increasing a configurable amount above the baseline value of the electro-hydraulic pump based on a torque signal. The process is repeated to determine the reverse starting value. Brief Description of the Drawings

[0016] Figure 1 is a schematic diagram of the environment of a system for calibrating an electro-hydraulic pump; and

[0017] Figure 2 It is a flowchart of a system for calibrating an electro-hydraulic pump. Detailed implementation

[0018] Referring to the accompanying drawings, a system 10 for calibrating the starting current of an electro-hydraulic pump based on an engine output torque signal includes a vehicle or machine 12 having a propulsion system 14. The propulsion system 14 includes an engine 16 connected to an electro-hydraulic pump 18. Although any number of pump control type applications and vehicle applications may be used, preferably, the system is used with a Non-Feedback Proportional Electric (NFPE) control pump commonly used in automotive control systems implemented on construction vehicles such as wheel loaders, telehandlers, dumpers, etc.

[0019] The system 10 also includes a microcontroller 20 with software 22, an input device 24 (such as a drive pedal), and a sensor 26. Although any type of sensor 26 may be used, preferably, it is a load sensor present in modern vehicles with electronically controlled engines. In some examples, there is no physical load or torque sensor, but instead, the signal is internally calculated or estimated by the engine control unit 20 (ECU). The software uses multiple parameters to convert an internal analog drive signal into an analog output signal to control the movement of the pump 18 and the machine 12. Among these parameters are a forward starting current value and a reverse starting current value. The starting current value is a particularly important parameter because it is used to stroke the pump and move the vehicle when the operator controls the input device 24.

[0020] In operation, in the event of a failure where the vehicle 12 may unexpectedly move, even if it is likely to move at a relatively low ground speed, initial safety precautions should be taken. For example, restrain the vehicle to the ground with safety chains, place it directly in front of an immovable wall or other object, or lift the wheels into the air. Then start the vehicle 12 and keep the vehicle 12 in a stationary position throughout the process. With the operator seated in the cab, the calibration process is started by pressing a button 28 on a dedicated display screen or service tool 30 in the cab. For accuracy, the engine crankcase oil temperature and the hydraulic oil temperature must start within a configurable range before the process can continue, otherwise the process will abort. This prevents the process from being carried out under extreme conditions that may affect the accuracy of the measurement.

[0021] The traction drive is automatically placed in a low torque condition by software 22. To achieve this, software 22 commands the hydraulic motor 32 to its minimum displacement, typically 20% to 25% or as low as 0% of the displacement of the hydraulic motor, switches the multi-speed gearbox (if present) to the highest gear, automatically applies or requests manual application of the parking brake, and requires the operator to always press and hold the service brake pedal. This process involves running a blocked port program on vehicle 12, where the traction drive output of the vehicle is held stationary by its on-board braking system, and the pump command current is increased from a lower starting value until the displacement of the pump increases. During this process, any flow is pumped into a dead volume and is not consumed by any connected working device such as hydraulic motor 32.

[0022] The accuracy of this process depends on all torque loads on the engine (except for the torque from the propulsion pump being calibrated) to remain relatively constant. To avoid inaccuracies, any variable loads from other sources such as an AC compressor, an open circuit pump, or other auxiliary loads should be disabled or kept deactivated until the process is complete. If auxiliary load activity is detected, such as movement of a joystick or steering wheel, or if the engine load measurement is constantly changing at an unacceptable rate or by an unacceptable amount, the process will abort.

[0023] With safety considerations in mind and when the start conditions are met, when the pump is not commanded, the engine 16 is commanded by software to a constant speed value to generate a baseline engine load that can be measured. In an automotive control system, the commanded speed value reflects the engine speed for initial desired movement on low resistance terrain and is referred to as the starting speed. The baseline load value represents the load required to overcome the internal drag torque of the engine and any constant auxiliary loads. Modern engines with an electronic control unit (ECU) typically output two signals indicating the engine load. For example, according to the J1939 CAN standard engine, these two signals are called "Actual Engine-Percent Torque" and "Engine Percent Load at Speed". These signals are instantaneous estimates of the actual torque output of the engine and are present in almost all modern vehicles with a diesel engine. Any one of these signals can be reliably used as a reference torque signal for this process.

[0024] Next, the pump current is ramped up at a configurable rate (mA / s) to a configurable minimum value (mA) by software 22. This minimum value should typically be set slightly below the normal starting current range of the pump, and optionally, the pump control orientation and / or the oil temperature can be considered, both of which have an impact. As the pump current increases, the pump will enter the stroke at some point and start building system pressure as the pump pumps against the stationary motor. The simultaneous increase in displacement and pressure increases the load torque on the pump and the engine, which will be represented as an increase in the engine load signal. Once the load torque signal increases by a configurable amount above the baseline value, the pump current value is stored as the starting current in the microcontroller 20. Then, an increase in engine torque by a specified amount is considered to indicate that the starting current for this direction of the pump has been reached. Then the process is repeated for the other direction of the pump, and then the entire process is considered complete. More specifically, when the pump current to the no-feedback proportional electro (NFPE) control ramps up from the minimum value, it reaches a value that actuates the valve and increases the pressure in the servo system. The servo pressure in the pump eventually increases to a value that causes the swashplate of the pump to rotate and the pump to enter the stroke, thereby increasing the pump displacement. As the pump displacement increases and flow is generated against the stationary motor, the system pressure increases. The simultaneous increase in system pressure and pump displacement requires an increase in the driving torque of the prime mover (the engine in this example).

[0025] If desired, the process can be automatically repeated a configurable number of times to ensure consistency between the calibration values on each side and to establish the final parameter values based on the average of multiple runs. Alternatively, the oil temperature measured during the process can be used to automatically compensate the final starting current value or adjust it up or down based on the known effect of temperature on oil viscosity.

[0026] If certain conditions are detected during the process, additional safety measures can be implemented. For example, if motor speed, the brake pedal being released, the parking brake being released, the operator leaving the seat, motor feedback or other motor position sensors indicating a commanded position other than minimum displacement, and / or the gearbox shifter indicating a gear position other than the highest gear are detected during the process, the process will automatically abort.

[0027] From the above discussion, as well as the drawings and claims, it can be understood that system 10 provides many advantages over the prior art. Those skilled in the art will further understand that various other different modifications can be made to the device without departing from the spirit and scope of the present invention. All such modifications and changes fall within the scope of the claims and are intended to be covered by the claims. It should be understood that the examples and embodiments described herein are for illustrative purposes only and will suggest various different modifications or changes to those skilled in the art in light of what they have obtained, and such various different modifications or changes are included within the spirit and scope of the present application.

Claims

1. A system for calibrating an electro-hydraulic pump, comprising: a machine having a propulsion system that includes an engine connected to the electro-hydraulic pump; a microcontroller connected to a sensor and having software and an input device; wherein the software has a calibration process that includes: the software is configured to command the engine to reach a constant speed and not command the electro-hydraulic pump to generate a baseline engine load and store the baseline engine load in the microcontroller; after generating the baseline engine load, the software is configured to command the electro-hydraulic pump to ramp up at a configurable rate to a configurable minimum until the electro-hydraulic pump enters a stroke, causing the engine load to increase above the baseline engine load; after the increase in the engine load reaches a configurable amount above the baseline engine load, the software is configured to determine a starting current value for one direction of the electro-hydraulic pump; wherein the software uses a plurality of parameters to convert an internal analog drive signal into an analog output signal to control the movement of the electro-hydraulic pump and the machine, and the parameters include a forward starting current value and a reverse starting current value.

2. The system according to claim 1, wherein, the sensor is a load sensor.

3. The system according to claim 1, wherein, the electro-hydraulic pump is a non-feedback proportional electro-control pump.

4. The system according to claim 1, wherein, when the input device is controlled by an operator, the starting current value causes the electro-hydraulic pump to enter a stroke.

5. The system according to claim 1, wherein, there is a button on the service tool for starting the calibration process.

6. The system according to claim 1, wherein, the software commands the hydraulic motor to reach a displacement between 0% and 25% before generating the baseline engine load.

7. The system according to claim 6, wherein, the software commands the hydraulic motor to reach a displacement between 20% and 25% before generating the baseline engine load.

8. The system according to claim 6, wherein, fluid is pumped into the dead volume and not consumed by the working device.

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