A front and rear axle independent drive loader vertical load estimation method

Abstract

The application provides a front and rear axle independent driving loader vertical load estimation method, which analyzes the front and rear axle vertical loads in the digging working condition and the driving working condition; in the digging working condition, the relationship between the pressure difference of the two cavities of the bucket cylinder under different loads and the front and rear axle vertical loads is constructed, and the front and rear axle vertical loads are correspondingly solved according to the real-time measured pressure difference of the two cavities of the bucket cylinder; in the driving working condition, the relationship between the different speeds and different loads and the front and rear wheel speed difference is constructed, and the relationship between the different loads and the front and rear axle vertical loads in the vehicle static state is constructed, the vehicle load is correspondingly solved according to the real-time measured front and rear wheel speed difference, and then the front and rear axle vertical loads are correspondingly solved according to the vehicle load. According to the above method, the front and rear axle vertical loads can be approximately solved, and the driving force distribution of the loader on the front and rear wheels can be calculated according to the vertical loads.

Description

Technical Field

[0001] This invention relates to loader technology, specifically to a method for estimating the vertical load of a loader with independent front and rear axle drive. Background Technology

[0002] Electric loaders significantly reduce pressure losses along the hydraulic lines, between valves, and during overflow due to the decoupling of the drive unit from the hydraulic system and the front and rear axle drive forces. This also eliminates parasitic power in the drive unit. Furthermore, the decoupling of independent front and rear axle drive and the hydraulic transmission also improves the efficiency of the electric motor.

[0003] However, due to the excessive axle load transfer when the loader is heavily loaded and unloaded, and the need to utilize the maximum static friction of the ground during loading and starting, wheel slippage occurs when the driving force of the axle with a small vertical load exceeds the maximum static friction that the axle load can provide, due to the decoupling of the front and rear axle driving forces. Conversely, when the driving force is evenly distributed among the heavy-load wheels, the maximum static friction provided by the axle load cannot be fully utilized, resulting in insufficient overall vehicle driving force. Patents CN202210331525.8 and CN202210331519.2 both propose configurations and driving force distribution methods for loaders with independent front and rear axle drives, where the driving force distribution depends on the loader's vertical load. However, the patents do not provide methods for calculating or determining the vertical load.

[0004] Existing research has found that loaders are all centrally driven, with mechanical coupling between the front and rear axles. Regardless of how the vertical load is transferred between the front and rear axles, it does not affect the utilization of the loader's maximum static friction force (maximum driving force). Therefore, existing research on loader loads focuses on the weight of the material being scooped, and often uses mechanical formulas based on the pressure difference between the two chambers of the boom to make judgments. However, in the loader's shoveling operation, the resistance caused by the material pile is much greater than the impact of the material weight on the pressure difference in the boom chamber, and this is the operating condition where the loader's maximum shoveling force is used. Therefore, it is necessary to select an effective method for estimating the front and rear axle loads under the maximum driving force condition of the loader, in order to distribute the driving force of a loader with independent front and rear axle drive. Summary of the Invention

[0005] To address existing problems, this invention provides a method for estimating the vertical load of a loader with independent front and rear axle drive, aiming to provide an accurate basis for the distribution of loader driving force. This method analyzes the influence of vehicle load and speed factors on wheel speed, axle vertical load, and the pressure difference between the two chambers of the bucket cylinder, establishing relationships to estimate the vertical loads of the front and rear axles under both vehicle driving and digging conditions.

[0006] The technical solution adopted in this invention is:

[0007] A method for estimating the vertical load of a front and rear axle independently driven loader, including estimating the vertical load of the front and rear axles under digging and driving conditions;

[0008] 1) Excavation working condition

[0009] Under digging conditions, by constructing the relationship between the pressure difference between the two chambers of the bucket cylinder and the vertical loads of the front and rear axles under different loads, the vertical loads of the front and rear axles are obtained based on the real-time measured pressure difference between the two chambers of the bucket cylinder.

[0010] 2) Driving conditions

[0011] Under driving conditions, by constructing the relationship between different vehicle speeds and different loads and the wheel speed difference between the front and rear wheels, as well as the relationship between different loads and the vertical loads of the front and rear axles when the vehicle is stationary, the vehicle load is calculated based on the real-time measured vehicle speed and the wheel speed difference between the front and rear wheels, and then the vertical loads of the front and rear axles are calculated based on the vehicle load.

[0012] Furthermore, in this method:

[0013] The method for establishing the relationship between the pressure difference between the two chambers of the bucket cylinder and the vertical loads of the front and rear axles under different loads during digging operations is as follows:

[0014] By loading different weights of material into the bucket several times, sampling points are used to determine the different loads on the vehicle.

[0015] Then, with the bucket just off the ground, the pressure difference between the two chambers of the bucket cylinder and the vertical loads on the front and rear axles were collected under different loads.

[0016] Then, the interpolation method was used to construct the functional relationship between the pressure difference between the two chambers of the bucket cylinder and the vertical loads of the front and rear axles.

[0017] Furthermore:

[0018] When the vehicle speed is zero, the vehicle load is 0% of the rated load, and the bucket is 10cm parallel to the ground, the pressure difference between the two chambers of the bucket cylinder is P. a ;

[0019] When the vehicle speed is zero, the vehicle load is 100% of the rated load, the bucket is retracted to its limit position, and the boom is raised to its limit position, the pressure difference between the two chambers of the boom cylinder is P. b ;

[0020] When the pressure difference between the two chambers of the loading boom cylinder is greater than P b The pressure difference between the two chambers of the bucket cylinder is greater than P. a When the vehicle speed is below 1 km / h, it is determined that the vehicle has entered the digging and excavation working condition.

[0021] Furthermore, in this method:

[0022] The method for establishing the relationship between different vehicle speeds and loads and the difference in wheel speed between the front and rear wheels under driving conditions is as follows:

[0023] By loading different weights of material into the bucket cylinder several times, load sampling points are established.

[0024] Then, with the front and rear tire pressures of the loader normal, the bucket cylinder retracted to its limit position, and the boom cylinder raising the bucket by 20-80cm, measure the difference in wheel speed between the front and rear wheels of the loader under different loads and vehicle speeds.

[0025] Then, the interpolation method is used to construct the functional relationship between different loads and vehicle speeds and the difference in wheel speed between the front and rear wheels;

[0026] The method for constructing the functional relationship between different loads on a vehicle under stationary conditions and the vertical loads on the front and rear axles is as follows:

[0027] By loading different weights of material into the bucket cylinder several times, load sampling points are established.

[0028] Then, with the front and rear tires of the loader in normal air pressure, the bucket cylinder retracted to its limit position, and the boom cylinder raising the bucket by 20-80cm, measure the vertical loads of the front and rear axles of the loader under different loads in a static state.

[0029] Then, the interpolation method is used to construct the functional relationship between the static load and the difference in wheel speed between the front and rear wheels.

[0030] Furthermore, in this method:

[0031] The number of times materials of different weights are filled is determined by the ability to construct a functional relationship using interpolation.

[0032] The beneficial effects of the present invention are: the vertical loads of the front and rear axles can be approximately obtained according to the above method; based on the magnitude and difference of the vertical loads, the maximum driving force available to the loader and its distribution on the front and rear wheels can be accurately calculated, thereby achieving precise control of the loader's driving force and essentially anti-skid control. Detailed Implementation

[0033] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments.

[0034] As can be seen from the loader load spectrum, the loader's maximum driving force occurs during the loader's digging and driving operations. Therefore, this invention focuses on analyzing the vertical loads on the loader's front and rear axles under these two conditions, while also considering all operating conditions of the loader.

[0035] Based on extensive experimental testing and structural analysis of the loader, the vertical load changes of the front and rear axles differ under the two working conditions, and their estimation methods are also different.

[0036] 1. Excavation working conditions

[0037] During the shoveling process, loaders are mainly subjected to the longitudinal resistance and vertical pressure of the material. Therefore, during shoveling, the loader's center of gravity shifts due to the vertical pressure of the material on the bucket, causing changes in the load on the front and rear axles, and consequently, the maximum driving force that the front and rear axles can provide. Thus, the load generated by the material during shoveling directly affects the pressure difference between the two chambers of the bucket cylinder, and the relationship between this pressure difference and the vertical loads on the front and rear axles can be determined using this pressure difference.

[0038] 1.1 Data Collection and Relationship Construction of Excavation Working Conditions

[0039] Under digging conditions, by loading different weights of material into the bucket as sampling points for different vehicle loads, the bucket teeth are positioned parallel to the ground with the bucket just off the ground (approximately 10 cm). The pressure difference between the two chambers of the bucket cylinder and the vertical loads on the front and rear axles are collected under different loads. As shown in Table 1, sampling points are selected with loads of 0%, 20%, 40%,... up to 200% of the rated load, increasing in 20% increments. The pressure difference between the two chambers of the bucket cylinder and the vertical loads on the front and rear axles are measured under these loads. Of course, other sampling point values ​​can also be selected, and the number of sampling points can be customized.

[0040] Table 1

[0041]

[0042] Then, based on the pressure difference between the two chambers of the bucket cylinder and the vertical loads of the front and rear axles at different load sampling points measured in the experiment, the interpolation method was used to construct the functional relationship between the pressure difference between the two chambers of the bucket cylinder and the vertical load of the front axle, as well as the functional relationship between the pressure difference between the two chambers of the bucket cylinder and the vertical load of the rear axle, under the condition of digging and excavating.

[0043] When the vehicle speed is zero, the load is 0% of the rated load, the lower surface of the bucket teeth is parallel to the ground, and the bucket is about 10cm off the ground, the pressure difference between the two chambers of the bucket cylinder is P. a ;

[0044] When the vehicle speed is zero, the load is 100% of the rated load, the bucket is retracted to its limit position, and the boom is raised to its limit position, the pressure difference between the two chambers of the boom cylinder is P. b .

[0045] 1.2 Estimation of Vertical Loads on the Axle Before and After Excavation

[0046] When the pressure difference between the two chambers of the loading boom cylinder is greater than P b The pressure difference between the two chambers of the bucket cylinder is greater than P. aWhen the vehicle speed is below 1 km / h, it is determined that it has entered the digging and excavating condition. Under the digging and excavating condition, based on the functional relationship between the vertical load of the front and rear axles and the pressure difference between the two chambers of the bucket cylinder, the vertical load of the front and rear axles is calculated according to the real-time measured pressure difference between the two chambers of the bucket cylinder.

[0047] 2. Driving conditions

[0048] When a vehicle is in operation, in addition to the changes in the vertical load on the axle caused by the vehicle load, the vehicle speed also affects the changes in the vertical load on the axle, and the vertical load on the axle is directly reflected in the wheel speed. Therefore, the vertical loads of the front and rear axles can be obtained by using the changes in the front and rear wheel speeds caused by changes in vehicle load and speed, as well as the relationship between vehicle load and axle vertical load.

[0049] 2.1 Data Collection and Relationship Building for Driving Conditions

[0050] With the front and rear tire pressures of the loader normal (tire pressure maintained within 1% of the rated pressure is considered normal), the bucket cylinder retracted to its limit position, and the bucket raised a certain distance (20-80cm, preferably 60cm) using the boom cylinder, the front and rear wheel speed differences under different loads and vehicle speeds, as well as the vertical loads on the front and rear axles under various loads when the vehicle is stationary, are calibrated. The front and rear wheel speed differences are obtained from feedback by the motor controller.

[0051] For example, as shown in Table 2, the vehicle load sampling points are selected as 0%, 20%, 40%, 60%, 80%, and 100% of the rated load, and the vehicle speed sampling points are selected as 20%, 40%, 60%, 80%, and 100% of the rated vehicle speed. Then, the front and rear wheel speed differences are measured at each load and each vehicle speed.

[0052] Terminology Explanation: Rated vehicle speed refers to the product of the front wheel motor speed and the static radius of the front wheel under no-load and rated air pressure.

[0053] For example, as shown in Table 3, when the vehicle is stationary, the vehicle load sampling points are selected as 0%, 20%, 40%, 60%, 80%, and 100% of the rated load, corresponding to the vertical loads of the front and rear axles.

[0054] The above sampling point values ​​can also be selected from other sampling point values, and the number of sampling points selected can also be customized.

[0055] Table 2

[0056]

[0057] Table 3

[0058]

[0059] Then, based on the experimental sampling data, the interpolation method was used to construct the functional relationship between different loads and vehicle speeds and the difference in wheel speeds between the front and rear wheels of the vehicle under driving conditions; the interpolation method was also used to construct the functional relationship between different loads and the vertical loads of the front and rear axles of the vehicle under stationary conditions.

[0060] 2.2 Estimation of vertical loads on the front and rear axles under driving conditions

[0061] Based on the functional relationship between different loads and vehicle speeds and the difference in wheel speed between the front and rear wheels of the vehicle, the vehicle load is first calculated using the real-time vehicle speed and the difference in wheel speed between the front and rear wheels. Then, the vertical loads of the front and rear axles are calculated using the functional relationship between different loads and the vertical loads of the front and rear axles.

Claims

1. A method for estimating the vertical load of a loader with independent front and rear axle drive, characterized in that: This includes estimating the vertical loads on the front and rear axles under both digging and driving conditions. 1) Excavation working condition Under digging conditions, the relationship between the pressure difference between the two chambers of the bucket cylinder and the vertical loads of the front and rear axles under different loads is constructed by collecting digging conditions data. Based on the real-time measured pressure difference between the two chambers of the bucket cylinder, the vertical loads of the front and rear axles are calculated accordingly. The method for constructing the relationship between the pressure difference between the two chambers of the bucket cylinder and the vertical loads of the front and rear axles under different loads is as follows: By loading different weights of material into the bucket several times, sampling points are used to determine the different loads on the vehicle. Then, with the bucket just off the ground, the pressure difference between the two chambers of the bucket cylinder and the vertical loads on the front and rear axles were collected under different loads. Then, the interpolation method was used to construct the functional relationship between the pressure difference between the two chambers of the bucket cylinder and the vertical loads of the front and rear axles; 2) Driving conditions Under driving conditions, the relationship between different vehicle speeds and loads and the wheel speed difference between the front and rear wheels is constructed by collecting driving condition data, as well as the relationship between different loads and the vertical loads of the front and rear axles when the vehicle is stationary. Based on the real-time measured vehicle speed and the wheel speed difference between the front and rear wheels, the vehicle load is calculated accordingly, and then the vertical loads of the front and rear axles are calculated based on the vehicle load. 2.1) The method for constructing the relationship between different vehicle speeds and loads and the difference in wheel speed between the front and rear wheels is as follows: By loading different weights of material into the bucket cylinder several times, load sampling points are established. Then, with the front and rear tire pressures of the loader normal, the bucket cylinder retracted to its limit position, and the boom cylinder raising the bucket by 20-80cm, measure the difference in wheel speed between the front and rear wheels of the loader under different loads and vehicle speeds. Then, the interpolation method is used to construct the functional relationship between different loads and vehicle speeds and the difference in wheel speed between the front and rear wheels; 2.2) The method for constructing the functional relationship between different loads on a vehicle under static conditions and the vertical loads on the front and rear axles is as follows: By loading different weights of material into the bucket cylinder several times, load sampling points are established. Then, with the front and rear tires of the loader in normal air pressure, the bucket cylinder retracted to its limit position, and the boom cylinder raising the bucket by 20-80cm, measure the vertical loads of the front and rear axles of the loader under different loads in a static state. Then, the interpolation method is used to construct the functional relationship between the static load and the vertical loads of the front and rear axles.

2. The method for estimating the vertical load of a front and rear axle independently driven loader according to claim 1, characterized in that: When the vehicle speed is zero, the vehicle load is 0% of the rated load, and the bucket is 10cm parallel to the ground, the pressure difference between the two chambers of the bucket cylinder is P. a ; When the vehicle speed is zero, the vehicle load is 100% of the rated load, the bucket is retracted to its limit position, and the boom is raised to its limit position, the pressure difference between the two chambers of the boom cylinder is P. b ; When the pressure difference between the two chambers of the loading boom cylinder is greater than P b The pressure difference between the two chambers of the bucket cylinder is greater than P. a When the vehicle speed is below 1 km / h, it is determined that the vehicle has entered the digging and excavation working condition.

3. The method for estimating the vertical load of a front and rear axle independently driven loader according to claim 1, characterized in that: The number of times materials of different weights are filled is determined by the ability to construct a functional relationship using interpolation.

Images