CN111674461A - Control method for full hydraulic power steering system - Google Patents
Control method for full hydraulic power steering system Download PDFInfo
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- CN111674461A CN111674461A CN202010580592.4A CN202010580592A CN111674461A CN 111674461 A CN111674461 A CN 111674461A CN 202010580592 A CN202010580592 A CN 202010580592A CN 111674461 A CN111674461 A CN 111674461A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
- B62D5/061—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle provided with effort, steering lock, or end-of-stroke limiters
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
- B62D5/065—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle characterised by specially adapted means for varying pressurised fluid supply based on need, e.g. on-demand, variable assist
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D6/00—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits
- B62D6/008—Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications
Abstract
A control method for an all hydraulic power steering system, comprising the steps of: (1) the steering wheel angle sensor collects steering wheel angle signals, and the vehicle speed sensor collects vehicle speed v when the steering wheel rotates1(ii) a (2) Converting the collected steering wheel angle into a designed wheel angle according to the proportional relation between the steering wheel angle and the wheel angle1(ii) a (3) The electronic control unit calculates the given designed wheel rotation angle1And a given vehicle speed v1Ideal centroid side deflection angle β of dump truck for lower mine1(ii) a (4) Obtaining actual wheel rotation angle by wheel rotation angle sensor2The vehicle speed v during the rotation of the wheel is acquired by a vehicle speed sensor2And calculating the given vehicle speed v through the electric control unit2In the case of making the actual centroid slip angle β2Is close to or equal to the ideal centroid slip angle β1Desired target wheel angle3(ii) a (5) Adjusting the oil supply of the steering system in real time to make the actual wheel turn angle2Approaching or equal to the target wheel angle3. The method can guarantee the steering accuracy and the vehicle running stability.
Description
Technical Field
The invention relates to the technical field of steering systems of mining dump trucks, in particular to a control method for a full hydraulic power steering system.
Background
In recent years, with the rapid economic development of China, neighboring countries and countries in Africa, the ore industry keeps a good growth trend, and the construction of various mines, especially large open-pit mines, is well-developed, and the yield is also increased year by year. Because of high working efficiency of the heavy-duty mining dump truck, a plurality of large-scale surface mines also use the heavy-duty mining dump truck as a main transport tool, and the number of the heavy-duty mining dump trucks is continuously increased. The whole mining dump truck has large mass and large front axle load, so the steering of the front wheels completely depends on hydraulic power.
The full hydraulic power steering system for the mining dump truck adopts a small-displacement steering gear as pilot control, most of oil is sent to a steering power cylinder through a flow amplifier, and the full hydraulic power steering system has the characteristics of small operating force and proportional outflow flow to the steering wheel rotation angle. As shown in the following formula:
qA＝KVn；
in the formula, K is the amplification factor of the flow amplifier, V is the displacement of the steering gear, and n is the rotating speed of the steering wheel.
The specific working principle is as follows: the driver operates the steering wheel, and controls the flow of the oil entering the steering power cylinder by rotating the rotary valve of the full hydraulic steering gear, so that the extension or the contraction of a piston rod in the steering power cylinder is pushed, and the steering piston rod pushes a steering knuckle to enable wheels to rotate around a steering main pin.
When the mining dump truck travels in a straight line, the oil pressure of two cavities of the steering power cylinder is equal. When the steering engine rotates leftwards, high-pressure oil enters a rodless cavity of the left steering power cylinder and a rod cavity of the right steering power cylinder; when the steering mechanism turns right, high-pressure oil enters a rod cavity of the left steering oil cylinder and a rodless cavity of the right steering oil cylinder, and the steering oil cylinder enables wheels to steer under the pushing of the high-pressure oil. If emergency (such as diesel engine failure) occurs, the reliable steering accumulator provides pressure oil for left and right full steering, but the pressure oil of the accumulator only allows short-time operation, otherwise, the steering can not be performed because of pressure drop.
The steering power is provided by a steering hydraulic pump. Compared with other steering systems, the full hydraulic steering system cancels the mechanical connection between the steering wheel and the steering wheel, replaces the hydraulic pipeline connection, and has the advantages of light and flexible operation, compact structure, easy installation and arrangement, capability of ensuring the steering performance when an engine is flamed out, and the like.
However, the existing full hydraulic power steering system has the following defects:
1) at any vehicle speed, the volume of oil discharged by the full hydraulic steering gear is in direct proportion (linear relation) to the rotation angle of the steering wheel, namely the displacement of a steering piston rod is in direct proportion to the rotation angle of the steering wheel. Due to the space geometric motion relationship of the steering mechanism, the rotation angle of the front wheel and the rotation angle of the steering wheel are in a nonlinear relationship, and the accuracy of the pre-judgment of the driver is influenced.
2) The full hydraulic power steering system has no feedback control. The full hydraulic steering gear is typically controlled in an open loop mode, deviation or interference (such as oil leakage) occurs in any link in a transmission process, the precision and stability of a system are affected, and the stability of straight line driving and the flexibility of steering driving cannot be guaranteed.
Therefore, improvements are needed.
Disclosure of Invention
The invention aims to provide a control method for a full hydraulic power steering system, which enables the steering wheel angle and the wheel angle to meet the linear relation, and the actual angle of the wheel can reach the expected angle during design. In order to achieve the purpose, the invention adopts the following technical scheme:
a control method for an all hydraulic power steering system, comprising the steps of:
(1) the steering wheel angle sensor collects steering wheel angle signals, and the vehicle speed sensor collects vehicle speed v when the steering wheel rotates1；
(2) Converting the collected steering wheel angle into a designed wheel angle according to the proportional relation between the steering wheel angle and the wheel angle1；
(3) The electronic control unit calculates the given designed wheel rotation angle1And a given vehicle speed v1Ideal centroid side deflection angle β of dump truck for lower mine1；
(4) Obtaining actual wheel rotation angle by wheel rotation angle sensor2The vehicle speed v during the rotation of the wheel is acquired by a vehicle speed sensor2And calculating the given vehicle speed v through the electric control unit2In the case of making the actual centroid slip angle β2Is close to or equal to the ideal centroid slip angle β1Desired target wheel angle3；
(5) The oil supply quantity of a steering system is adjusted in real time through an electric control unit, so that the actual wheel turning angle2Approaching or equal to the target wheel angle3。
Further, the ideal centroid slip angle β1The calculation formula of (a) is as follows:
①：
in the above formula, Cf、CrRepresenting the cornering stiffness of the front and rear tires, L being the wheelbase, a and b representing the distance from the center of mass of the whole vehicle to the front and rear axles, vx1Is the vehicle speed v1The component of the centroid velocity on the x-axis, m, represents the vehicle mass.
Further, the actual centroid slip angle β2Is close to or equal to the ideal centroid slip angle β1When, the actual centroid slip angle β2The calculation formula of (a) is as follows:
②：
wherein v isx2Is the vehicle speed v2The component of the centroid velocity on the x-axis;
further, β2＝β1To find a target wheel turning angle3；Δ＝3-2；
And adjusting the oil supply amount of the steering system according to the delta.
Further, the ideal centroid slip angle β1Equal to or close to 0.
Further, β2＝0；
Further, in the above-mentioned case,
③：
④：ω3≤ωr,max
in formula ③, [ omega ]3Is β3Ideal yaw rate when equal to 0, ωr,maxThe yaw-rate maximum value.
Furthermore, as can be seen from the slip ratio-adhesion coefficient curve, the lateral adhesion coefficient of the road surface has different values under different slip ratios, the lateral force has different values under different lateral adhesion coefficients, and the saturation value F of the lateral forcey,maxAs well as changes. The maximum value of the road adhesion coefficient determines the maximum tire lateral and longitudinal forces that can be provided by the ground, and therefore the desired yaw rate is also limited by the adhesion relationship between the tire and the road. Maximum tire lateral force:
Fy,max＝may,max＝mνmaxg；
wherein, vmaxThe maximum value of the component of the centroid velocity on the x-axis, so the ideal maximum yaw-rate is:
further, considering that there should be a certain adhesion margin in actual operation, the maximum value of the yaw rate satisfies the following relationship:
furthermore, the full hydraulic power steering system comprises a full hydraulic power steering gear, a flow amplifier, a steering power cylinder, a steering wheel angle sensor for detecting the steering wheel angle, a wheel angle sensor for detecting the wheel angle, a vehicle speed sensor for detecting the real-time vehicle speed and an electric control unit.
By adopting the technical scheme, the front wheel corner and the driver steering wheel corner meet the linear relation through active control, and the control difficulty of the driver is reduced.
And the yaw angular velocity and the centroid slip angle are used as control targets, so that the running stability of the vehicle is guaranteed.
The feedback control of the flow is realized, and the robustness of the full hydraulic power steering system under the non-ideal conditions of oil leakage and the like is improved.
Drawings
FIG. 1 is a schematic diagram of a two-degree-of-freedom vehicle model.
Detailed Description
The invention is described below with reference to the accompanying drawings and specific embodiments.
A full hydraulic power steering system comprises a full hydraulic power steering gear, a flow amplifier, a steering power cylinder, a steering wheel angle sensor for detecting the steering wheel angle, a wheel angle sensor for detecting the wheel angle, a vehicle speed sensor for detecting the real-time vehicle speed and an electric control unit.
A control method for an all hydraulic power steering system, comprising the steps of:
(1) steering wheel angle sensor collects steering wheel angle signals, and vehicle speed sensor collects steering wheel rotationVehicle speed v1；
(2) Converting the collected steering wheel angle into a designed wheel angle according to the proportional relation between the steering wheel angle and the wheel angle1；
(3) The electronic control unit calculates the given designed wheel rotation angle1And a given vehicle speed v1Ideal centroid side deflection angle β of dump truck for lower mine1；
(4) Obtaining actual wheel rotation angle by wheel rotation angle sensor2The vehicle speed v during the rotation of the wheel is acquired by a vehicle speed sensor2And calculating the given vehicle speed v through the electric control unit2In the case of making the actual centroid slip angle β2Is close to or equal to the ideal centroid slip angle β1Desired target wheel angle3；
(5) The oil supply quantity of a steering system is adjusted in real time through an electric control unit, so that the actual wheel turning angle2Approaching or equal to the target wheel angle3。
Ideal centroid slip angle β1The calculation formula of (a) is as follows:
①：
in the above formula, Cf、CrRepresenting the cornering stiffness of the front and rear tires, L being the wheelbase, a and b representing the distance from the center of mass of the whole vehicle to the front and rear axles, vx1Is the vehicle speed v1The component of the centroid velocity on the x-axis, m, represents the vehicle mass.
Actual centroid slip angle β2Is close to or equal to the ideal centroid slip angle β1When, the actual centroid slip angle β2The calculation formula of (a) is as follows:
②：
wherein v isx2Is the vehicle speed v2The component of the centroid velocity on the x-axis;
β2＝β1to find out the eyesCorner of road wheel3；
Δ＝3-2The amount of fuel supply to the steering system is adjusted according to the delta.
In the operation process of the mining dump truck, the condition that the centroid slip angle is zero is the optimal condition, and the ideal centroid slip angle β1Equal to or close to 0.
The derivation modes of the above formulas (i) and (ii) are as follows:
in each evaluation index of the operation stability, the parameters which can represent the operation stability of the mining dump truck most are a yaw velocity and a centroid slip angle, wherein in the two parameters, the yaw velocity reflects the capability of the mining dump truck whether to keep stable running, and the centroid slip angle reflects the track tracking capability of the mining dump truck. The final aim of improving the operation stability of the mining dump truck is to maintain the stability during track tracking. Therefore, the control method simplifies the mining dump truck into a two-degree-of-freedom model with only lateral motion along y and yaw motion around the Z axis, as shown in figure 1, takes a two-degree-of-freedom whole truck model as a reference model,
the two-degree-of-freedom vehicle model is as follows:
in the above formula, Cf、CrShowing the cornering stiffness of the front and rear tires, FY1, FY2 are the lateral forces to which the front and rear wheels are subjected, α1、α2Front and rear wheel slip angles; l is the wheelbase, and a and b represent the distance from the center of mass Cm of the whole vehicle to the front axle and the rear axle; v is the speed of the center of mass, vxIs the component of the centroid velocity in the x-axis, vyM is the mass center speed component on the y axis, m represents the whole vehicle mass and is the front wheel rotation angle, ξ is the heading angle, β is the mass center slip angle, omega is the vehicle yaw speed, IzThe moment of inertia of the mining dump truck around the Z axis is obtained.
Converting the above equation to a state space model is:
and (3) further analyzing the two-degree-of-freedom finished automobile model to obtain a mass center lateral deviation angle value beta when the mining dump truck is in steady-state steering:
bringing into correspondence vxAnd, the calculation formulas (formula ① and formula ②) of the corresponding centroid slip angle β are obtained.
When β3When equal to 0, and carry vx2And3：
③：
in formula ③, [ omega ]3Is β3The ideal yaw rate when the yaw rate is 0,
according to the slip rate-adhesion coefficient curve, the lateral adhesion coefficient of the road surface has different values under different slip rates, the lateral force has different values under different lateral adhesion coefficients, and the saturation value F of the lateral forcey,maxAs well as changes. The maximum value of the road adhesion coefficient determines the maximum tire lateral and longitudinal forces that can be provided by the ground, and therefore the desired yaw rate is also limited by the adhesion relationship between the tire and the road. Maximum tire lateral force:
Fy,max＝may,max＝mνmaxg；
wherein, vmaxThe maximum value of the component of the centroid velocity on the x-axis, so the ideal maximum yaw-rate is:
further, considering that there should be a certain adhesion margin in actual operation, the maximum value of the yaw rate satisfies the following relationship:
ω3≤ωr,max；
by adopting the technical scheme, the front wheel corner and the driver steering wheel corner meet the linear relation through active control, and the control difficulty of the driver is reduced.
And the yaw angular velocity and the centroid slip angle are used as control targets, so that the running stability of the vehicle is guaranteed.
The feedback control of the flow is realized, and the robustness of the full hydraulic power steering system under the non-ideal conditions of oil leakage and the like is improved.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the present invention, as it will be apparent to those skilled in the art that various modifications, combinations and variations can be made in the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (10)
1. A control method for a full hydraulic power steering system, characterized by: the method comprises the following steps:
(1) the steering wheel angle sensor collects steering wheel angle signals, and the vehicle speed sensor collects vehicle speed v when the steering wheel rotates1；
(2) Converting the collected steering wheel angle into a designed wheel angle according to the proportional relation between the steering wheel angle and the wheel angle1；
(3) The electronic control unit calculates the given designed wheel rotation angle1And a given vehicle speed v1Ideal centroid side deflection angle β of dump truck for lower mine1；
(4) Obtaining actual wheel rotation angle by wheel rotation angle sensor2The vehicle speed v during the rotation of the wheel is acquired by a vehicle speed sensor2And calculating the given vehicle speed v through the electric control unit2In the case of making the actual centroid slip angle β2Is close to or equal to the ideal centroid slip angle β1Desired target wheel angle3；
(5) Tong (Chinese character of 'tong')The electric control unit adjusts the oil supply quantity of the steering system in real time to make the actual wheel turn angle2Approaching or equal to the target wheel angle3。
2. The control method for a full hydraulic power steering system according to claim 1, wherein said ideal centroid slip angle β1The calculation formula of (a) is as follows:
①：
in the above formula, Cf、CrRepresenting the cornering stiffness of the front and rear tires, L being the wheelbase, a and b representing the distance from the center of mass of the whole vehicle to the front and rear axles, vx1Is the vehicle speed v1The component of the centroid velocity on the x-axis, m, represents the vehicle mass.
3. The control method for a full hydraulic power steering system according to claim 2, wherein the actual centroid slip angle β2Is close to or equal to the ideal centroid slip angle β1When, the actual centroid slip angle β2The calculation formula of (a) is as follows:
②：
wherein v isx2Is the vehicle speed v2The component of the centroid velocity on the x-axis.
4. The control method for an all-hydraulic power steering system according to claim 3, characterized in that:
β2＝β1to find a target wheel turning angle3；
Δ＝3-2；
And adjusting the oil supply amount of the steering system according to the delta.
5. The composition of claim 1 for use in whole fluidsThe control method of the pressure power steering system is characterized in that the ideal centroid slip angle β1Equal to or close to 0.
6. The control method for a full hydraulic power steering system according to claim 4, wherein β2＝0。
7. The control method for an all-hydraulic power steering system according to claim 6, characterized in that:
③：
④：ω3≤ωr,max；
in formula ③, [ omega ]3Is β3Ideal yaw rate when equal to 0, ωr,maxThe yaw-rate maximum value.
8. The control method for an all-hydraulic power steering system according to claim 7, characterized in that:
according to the slip rate-adhesion coefficient curve, the lateral adhesion coefficient of the road surface has different values under different slip rates, the lateral force has different values under different lateral adhesion coefficients, and the saturation value F of the lateral forcey,maxAs well as changes. The maximum value of the road adhesion coefficient determines the maximum tire lateral and longitudinal forces that can be provided by the ground, and therefore the desired yaw rate is also limited by the adhesion relationship between the tire and the road. Maximum tire lateral force:
Fy,max＝may,max＝mνmaxg；
wherein, vmaxThe maximum value of the component of the centroid velocity on the x-axis, so the ideal maximum yaw-rate is:
9. the control method for an all-hydraulic power steering system according to claim 8, characterized in that: considering that there should be a certain adhesion margin in actual operation, the maximum value of the yaw rate satisfies the following relationship:
10. the control method for an all-hydraulic power steering system according to claim 1, characterized in that: the full hydraulic power steering system comprises a full hydraulic power steering gear, a flow amplifier, a steering power cylinder, a steering wheel angle sensor for detecting the steering wheel angle, a wheel angle sensor for detecting the wheel angle, a vehicle speed sensor for detecting the real-time vehicle speed and an electric control unit.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101357648A (en) * | 2007-08-02 | 2009-02-04 | 日产自动车株式会社 | Vehicle steering control apparatus |
| CN101537853A (en) * | 2009-03-04 | 2009-09-23 | 长安大学 | Automobile four-wheel active steering control system |
| CN105151117A (en) * | 2015-08-28 | 2015-12-16 | 南京航空航天大学 | Electronically controlled hydraulic power steering system and multi-objective optimization method based on system |
| CN106004857A (en) * | 2015-03-30 | 2016-10-12 | 富士重工业株式会社 | Driving support system for vehicle |
| CN109017974A (en) * | 2018-07-02 | 2018-12-18 | 南京航空航天大学 | Assist steering system and its control method with active steering function |
| US20190092330A1 (en) * | 2017-09-28 | 2019-03-28 | Toyota Jidosha Kabushiki Kaisha | Vehicle driving support apparatus |
-
2020
- 2020-06-23 CN CN202010580592.4A patent/CN111674461B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101357648A (en) * | 2007-08-02 | 2009-02-04 | 日产自动车株式会社 | Vehicle steering control apparatus |
| CN101537853A (en) * | 2009-03-04 | 2009-09-23 | 长安大学 | Automobile four-wheel active steering control system |
| CN106004857A (en) * | 2015-03-30 | 2016-10-12 | 富士重工业株式会社 | Driving support system for vehicle |
| CN105151117A (en) * | 2015-08-28 | 2015-12-16 | 南京航空航天大学 | Electronically controlled hydraulic power steering system and multi-objective optimization method based on system |
| US20190092330A1 (en) * | 2017-09-28 | 2019-03-28 | Toyota Jidosha Kabushiki Kaisha | Vehicle driving support apparatus |
| CN109017974A (en) * | 2018-07-02 | 2018-12-18 | 南京航空航天大学 | Assist steering system and its control method with active steering function |
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