CN-121990048-A - MPC-based forklift steering state following control system and method

CN121990048ACN 121990048 ACN121990048 ACN 121990048ACN-121990048-A

Abstract

The invention discloses a forklift steering state following control system and method based on MPC, belonging to the field of heavy electric forklifts, comprising a steering manual control unit, a steering control unit, a control unit and a control unit, wherein the steering manual control unit is configured to collect a target steering angle instruction of a driver and provide torque feedback; the system comprises a steering manual control unit, an MPC (MPC) controller, a steering executing mechanism and a driving mechanism, wherein the steering manual control unit is in communication connection with the MPC controller to receive the target steering angle instruction, and based on a preset forklift steering system dynamics model, a current system state and a system constraint condition, the MPC controller is used for solving an optimal control increment sequence in a future limited time domain through rolling optimization, and the steering executing mechanism is electrically connected with the MPC controller to receive a control instruction at the current moment output by the MPC controller and drive a rear steering wheel of a forklift to rotate along with the target steering angle instruction. The robustness and the safety of the system under the limit working condition are improved, the energy efficiency of the whole vehicle is optimized, and the steering control is improved from passive error correction to active track prediction and optimization control.

Inventors

BI SHENG
WU MENG
HUANG JIANFENG
ZHANG HONGKAI
CHEN HUIHUI
CHEN FEI
XUE ZHENJIAN

Assignees

安徽合力股份有限公司

Dates

Publication Date: 20260508
Application Date: 20260318

Claims (11)

1. The utility model provides a fork truck turns to state follow control system based on MPC, is applied to heavy electric fork truck, characterized in that includes: a steering manual control unit (100) configured to collect a target steering angle command of a driver and provide torque feedback; An MPC controller (200) communicatively coupled to the steering hand control unit (100) to receive the target steering angle command and to solve an optimal control increment sequence in a future limited time domain by roll optimization based on a preset forklift steering system dynamics model, a current system state, and system constraints, and The steering executing mechanism is electrically connected with the MPC controller (200) to receive a control instruction of the current moment output by the MPC controller (200) and drive a rear steering wheel (350) of the forklift to rotate along with the target corner instruction.
2. The MPC-based forklift steering state follow control system of claim 1, wherein the steering actuator comprises: An oil supply unit; A steering ratio control valve group (320) connected with the oil supply unit, wherein the steering ratio control valve group (320) comprises a first steering valve (321) and a second steering valve (322) which are arranged in parallel; the steering oil cylinder (330) is a double-acting oil cylinder, and two cavities of the double-acting oil cylinder are respectively and independently connected with the first steering valve (321) and the second steering valve (322) so as to independently supply oil to the two cavities; And the rotation angle detection units (341, 342) are in communication connection with the MPC controller (200) so as to feed back the detected actual rotation angle to the MPC controller (200).
3. The MPC-based forklift steering state follow-up control system of claim 2, wherein the MPC controller (200) is configured to: Taking the target steering angle command, the rear steering wheel estimated steering angle, the rear steering wheel estimated angular velocity and the control currents of the first steering valve (321) and the second steering valve (322) as system state vectors; Predicting system output at N sampling moments in the future based on the system state vector and the fork truck steering system dynamics model; constructing and solving an optimal control increment sequence in M future control time domains for minimizing a cost function, wherein M is less than or equal to N, and the cost function at least comprises a penalty term for steering following errors; extracting a first element from the optimal control delta sequence obtained by solving Combining the control quantity of the previous moment Generating an actual control amount at the current time 。
4. The MPC-based forklift steering state follow-up control system of claim 3, wherein the system constraint conditions include at least one or more of a maximum opening constraint of the valve ports of the first steering valve (321) and the second steering valve (322), a stroke constraint of the steering cylinder (330), and a maximum rotation angle constraint of the rear steering wheel (350) in the construction and solving process of the cost function.
5. The MPC-based forklift steering state follow control system of claim 3, wherein the actual control amount at the present time Comprises a first independent opening instruction which is respectively distributed to the first steering valve (321) and a second independent opening instruction which is distributed to the second steering valve (322) so as to independently control the flow and the direction of hydraulic oil entering the cavities at two sides of the steering oil cylinder (330).
6. The MPC-based forklift steering state follow-up control system of claim 1, wherein the forklift steering system dynamics model is established based on experimental identification of forklift steering system key parameters, which at least include equivalent moment of inertia and equivalent damping coefficients.
7. The MPC-based forklift steering state follow control system of claim 1, wherein the MPC controller (200) is further configured to: And estimating a state vector under a continuous working condition at the current moment of the system according to the dynamic model of the forklift steering system and actual steering angles fed back by the steering angle detection units (341 and 342) through a state observer, wherein the state vector at least comprises an estimated steering angle and an estimated angular speed of a rear steering wheel (350).
8. The MPC-based forklift steering state follow control system of claim 3, wherein the steering hand control unit (100) comprises a fingertip steering controller (110) and a torque feedback device (120) coupled to each other, wherein the fingertip steering controller (110) is arranged at one side of a forklift seat.
9. The MPC-based forklift steering state follow-up control system of claim 8, wherein the MPC controller (200) is further communicatively coupled to the torque feedback device (120) and configured to generate a torque optimization command based on the solved optimal control delta sequence and send the torque optimization command to the torque feedback device (120) to optimize a torque output of a driver.
10. A method for MPC-based forklift steering state follow-up control applied to the system of any one of claims 1 to 9, comprising the steps of: s1, acquiring a target rotation angle instruction of a driver through a steering manual control unit (100); s2, acquiring the actual rotation angle of the rear steering wheel (350) in real time through rotation angle detection units (341, 342); S3, the MPC controller (200) receives the target corner instruction and the actual corner, and estimates a state vector of the system at the current moment by combining a preset forklift steering system dynamics model; S4, the MPC controller (200) predicts future system output by using a prediction model based on the target corner instruction and the estimated state vector, and solves an optimal control increment sequence in the future M control time domains for minimizing an optimal target function under the condition that a preset system constraint condition is met; S5, solving the S4 to obtain the first element in the optimal control increment sequence Control amount from the previous time Superposition to generate actual control quantity at current moment Wherein the actual control amount The hydraulic oil control device comprises independent opening instructions for respectively driving a first steering valve (321) and a second steering valve (322) so as to independently control the flow and the direction of hydraulic oil entering cavities at two sides of a steering oil cylinder (330); S6, the actual control quantity is calculated Transmitting to a steering actuator to drive a rear steering wheel (350) to follow the target steering angle command; And S7, repeatedly executing the steps S2 to S6 at the next sampling moment to form rolling optimization control.
11. The MPC-based forklift steering state follow-up control method of claim 10, wherein: in the step S3, the state vector of the current moment of the estimation system at least comprises the estimated rotation angle and the estimated angular velocity of the rear steering wheel (350); In the step S4, the prediction model is a forklift steering system dynamics model obtained based on experimental identification.

Description

MPC-based forklift steering state following control system and method Technical Field The invention relates to the technical field of heavy electric forklifts, in particular to a forklift steering state following control system and method based on MPC. Background The heavy electric forklift is used as core equipment in the field of logistics storage and industrial transportation, and the performance of a steering system of the heavy electric forklift directly determines the operation efficiency and the driving safety of the whole forklift. In order to meet the steering torque requirement under heavy load working conditions, the existing heavy forklift mostly adopts a hydraulic power steering system. However, the system has inherent defects of oil leakage risk, high energy consumption, response lag and the like. With the development of electric control technology, the steer-by-wire system is gradually applied to various vehicles. By canceling the mechanical connection between the steering wheel and the steering wheel, the intention of the driver is acquired by adopting a sensor, and the steering wheel is driven by a motor or an electrohydraulic actuator, so that the possibility is provided for realizing a more flexible steering control strategy. In the field of control of commercial vehicles such as semitrailers and heavy trucks, various methods based on modern control theory have been proposed for improving the stability of the commercial vehicles under high-speed or extreme conditions. For example, the chinese patent application publication No. CN116620307a discloses a method for controlling the longitudinal and transverse coordination during high-speed steering of an intelligent semi-trailer. According to the method, a nonlinear dynamics model of the semi-trailer is established, a nonlinear model predictive controller is designed, the front wheel rotation angle of the tractor and the braking moment of each wheel are cooperatively controlled, and the aim of inhibiting the folding and tail-flicking phenomena between the tractor and the trailer is achieved, so that the transverse stability of the whole vehicle is improved. The scheme reflects the advantages of model predictive control in processing the multi-constraint optimization problem by applying constraint to the control quantity and the increment thereof. However, the above prior art mainly focuses on stability control of a vehicle under a high-speed steering condition, and the control objective is to make the state of the whole vehicle tend to be stable, so as to avoid instability. For a specific industrial vehicle such as a heavy forklift, the core problem faced in actual operation is often not stability, but the following precision of a steering command. In particular, since heavy forklifts often employ rear-wheel steering and the operating conditions are variable (from idle high-speed driving to heavy low-speed inching), the steering system has significant nonlinearity and time-lag characteristics. This makes it difficult for the conventional control method or the simple angle correspondence algorithm to ensure accurate and rapid matching of the steering wheel or fingertip controller rotation angle with the actual rotation angle of the rear steering wheel under all conditions, problems such as follow overshoot and response delay are easy to occur, the operation accuracy and the driving comfort are affected, and even potential safety hazards are buried. Furthermore, the prior art does not give any explicit teaching of how to deeply couple model predictive control with specific electro-hydraulic steering actuators of a forklift to achieve fine control of the steering process. Therefore, how to provide a control scheme capable of following the steering intention of a driver with high precision and fast response aiming at the nonlinear and time-lag characteristics of a steering system of a heavy forklift is a technical problem to be solved in the field. Disclosure of Invention The invention aims to solve the technical problem of how to provide a control scheme which has high precision and fast response and follows the steering intention of a driver aiming at the nonlinear and time-lag characteristics of a steering system of a heavy forklift. In order to solve the above technical problems, the first aspect of the present invention provides a forklift steering state following control system based on MPC, which is applied to a heavy electric forklift, and includes: A steering manual control unit configured to collect a target rotation angle instruction of a driver and provide torque feedback; The MPC controller is in communication connection with the steering manual control unit to receive the target steering angle instruction, and solves the optimal control increment sequence in the future limited time domain through rolling optimization based on a preset forklift steering system dynamics model, a current system state and a system constraint condition,