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CN111830992A - Force control method, device and wheeled robot of a wheeled robot - Google Patents

Force control method, device and wheeled robot of a wheeled robot Download PDF

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Publication number
CN111830992A
CN111830992A CN202010754582.8A CN202010754582A CN111830992A CN 111830992 A CN111830992 A CN 111830992A CN 202010754582 A CN202010754582 A CN 202010754582A CN 111830992 A CN111830992 A CN 111830992A
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force
wheel
speed
traction
control
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CN111830992B (en
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丁亮
黄澜
于兆玮
杨怀广
齐华囡
李楠
高海波
邓宗全
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Harbin Institute of Technology Shenzhen
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Harbin Institute of Technology Shenzhen
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D1/00—Control of position, course, altitude or attitude of land, water, air or space vehicles, e.g. using automatic pilots
    • G05D1/02—Control of position or course in two dimensions
    • G05D1/021—Control of position or course in two dimensions specially adapted to land vehicles
    • G05D1/0212—Control of position or course in two dimensions specially adapted to land vehicles with means for defining a desired trajectory
    • G05D1/0223—Control of position or course in two dimensions specially adapted to land vehicles with means for defining a desired trajectory involving speed control of the vehicle
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D1/00—Control of position, course, altitude or attitude of land, water, air or space vehicles, e.g. using automatic pilots
    • G05D1/02—Control of position or course in two dimensions
    • G05D1/021—Control of position or course in two dimensions specially adapted to land vehicles
    • G05D1/0276—Control of position or course in two dimensions specially adapted to land vehicles using signals provided by a source external to the vehicle

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  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Electric Propulsion And Braking For Vehicles (AREA)
  • Control Of Position, Course, Altitude, Or Attitude Of Moving Bodies (AREA)

Abstract

本发明涉及机器人技术领域，具体涉及一种轮式机器人的力控制方法、装置及轮式机器人。本发明所述轮式机器人的力控制装置，包括期望转速生成部，其用于根据车身的期望速度生成车轮的期望转速；期望牵引力生成部，其用于生成车轮的期望牵引力；期望车轮力矩生成部，其用于根据期望转速和期望牵引力生成车轮的期望力矩；转速误差生成部，其用于根据实时转速和期望转速生成转速误差；牵引力误差生成部，其用于根据实时牵引力和期望牵引力生成牵引力误差；控制律生成部，其用于根据牵引力误差、转速误差和期望力矩生成车轮力速混合控制律，车轮力速混合控制律用于车轮的力跟踪控制或者速度跟踪控制。

Figure 202010754582

The invention relates to the technical field of robots, in particular to a force control method and device of a wheeled robot and a wheeled robot. The force control device for a wheeled robot according to the present invention includes a desired rotational speed generating unit for generating a desired rotational speed of the wheel according to a desired speed of the vehicle body; a desired tractive force generating unit for generating a desired tractive force of the wheel; and a desired wheel torque generating unit a rotational speed error generating unit for generating a rotational speed error based on the real-time rotational speed and the desired rotational speed; a traction force error generating unit for generating a rotational speed error based on the real-time traction force and the desired traction force Traction force error; a control law generation unit for generating a wheel force-speed hybrid control law according to the traction force error, rotational speed error and desired torque, and the wheel force-speed hybrid control law is used for wheel force tracking control or speed tracking control.

Figure 202010754582

Description

Force control method and device of wheeled robot and wheeled robot
Technical Field
The invention relates to the technical field of robots, in particular to a force control method and device of a wheeled robot and the wheeled robot.
Background
In general, a complete machine is used as a controlled object for controlling the movement of a wheeled robot, but in a multi-wheeled robot, the movement of different wheels may be different during the movement, and the internal forces between the different wheels may interfere with each other, thereby causing a hindrance to the movement of each other, and reducing the driving efficiency of the wheeled robot.
Disclosure of Invention
The invention aims to improve the control of the wheeled robot, reduce the interference between different wheels and improve the driving efficiency of the wheeled robot.
In order to solve the above problems, the present invention provides a force control apparatus for a wheeled robot, including a rotation speed acquisition unit for acquiring a real-time rotation speed of a wheel; the force acquisition part is used for acquiring real-time traction of the wheel; a desired rotation speed generating section for generating a desired rotation speed of the wheel according to a desired speed of a vehicle body; a desired traction force generating section for generating a desired traction force of the wheel; a desired wheel torque generation section for generating a desired torque of the wheel in accordance with the desired rotation speed and the desired traction force; a rotation speed error generating unit for generating a rotation speed error from the real-time rotation speed and the desired rotation speed; a tractive effort error generation section for generating a tractive effort error from the real-time tractive effort and the desired tractive effort; and a control law generating unit configured to generate a wheel-force-speed hybrid control law for force tracking control or speed tracking control of the wheel, based on the traction error, the rotational speed error, and the desired torque.
Optionally, the real-time rotational speed and the desired rotational speed are used for negative feedback adjustment of the wheel rotational speed.
Optionally, the real-time traction and the desired traction are used for negative feedback adjustment of the desired traction of the wheel.
Optionally, there are a plurality of pairs of the wheels, and the wheel force and speed hybrid control law is used for performing rotational speed tracking control on one pair of the wheels and performing traction tracking control on the remaining wheels so as to realize speed control on the vehicle body, so that the mutual blocking acting force between different wheels is minimized.
Optionally, the control system further comprises a rotation speed switch matrix generating part, configured to generate a rotation speed error combination matrix, and the control law generating part further determines whether to perform rotation speed tracking control on the wheel according to the rotation speed error combination matrix; the control law generating unit further determines whether to perform traction tracking control on the wheel based on the traction error combination matrix.
Optionally, the control law generating unit further performs rotation speed tracking control or traction tracking control on the wheel according to the error combination matrix.
Optionally, the system further comprises a speed acquisition part for acquiring the real-time speed of the vehicle body; the real-time speed and the desired speed are used for negative feedback adjustment of the body speed.
Optionally, the force acquisition unit is further configured to acquire a real-time normal force of the wheel, and further includes a force distribution generation unit configured to generate a force distribution matrix according to the real-time traction force and the real-time normal force, and the expected traction force generation unit is further configured to generate expected traction forces of different wheels according to the force distribution matrix.
Compared with the prior art, the force control device of the wheeled robot has the advantages that:
the method comprises the steps of acquiring real-time rotating speed and real-time traction of wheels, generating expected torque of the wheels according to the expected rotating speed and the expected traction, generating a force-speed hybrid control law of the wheels through rotating speed errors, traction errors and the expected torque, and tracking and controlling force or speed of the wheels through the force-speed hybrid control law, so that force-speed hybrid control of the wheels of the wheel type robot is realized, switching of force control or speed control of a control mode of the wheel type robot is facilitated, and driving efficiency of the wheels is improved.
The invention respectively determines the force control law or the speed control law of a single wheel based on the single wheel, performs force control on one pair of wheels of the wheel type robot and performs speed control on other wheels, avoids performing force control or speed control on all wheels of the wheel type robot at the same time, and reduces mutual obstruction among different wheels. Particularly, on soft ground, the stress condition of the wheels changes, the force of the wheels is tracked in real time, the tracking error caused by pure speed tracking is prevented from becoming larger and larger, and the tracking error can be converged to zero by tracking the speeds of other wheels and correcting the track.
The invention also provides a force control method of the wheeled robot, which comprises the following steps:
acquiring the real-time rotating speed and the real-time traction of a wheel; generating a desired rotational speed of the wheel according to a desired speed of a vehicle body; obtaining a desired traction of the wheel;
generating a desired torque for the wheel based on the desired speed and the desired traction;
generating a rotation speed error according to the real-time rotation speed and the expected rotation speed; generating a tractive effort error as a function of the real-time tractive effort and the desired tractive effort;
and generating a wheel force-speed hybrid control law according to the traction error, the rotating speed error and the expected torque, wherein the wheel force-speed hybrid control law is used for the wheel force-speed hybrid control.
Optionally, the vehicle further includes a plurality of pairs of wheels, and the method further includes performing rotational speed tracking control on one pair of wheels according to the wheel force and speed hybrid control law, and performing traction tracking control on the remaining wheels to achieve speed control on the vehicle body, so that the interaction blocking acting force between different wheels is minimized.
Optionally, determining a rotation speed error combination matrix, and judging whether to perform rotation speed tracking control on the wheel according to the rotation speed error combination matrix; and determining a traction error combination matrix, and judging whether to carry out traction tracking control on the wheel according to the traction error combination matrix.
Optionally, determining an error combination matrix, and performing rotation speed tracking control or traction tracking control on the wheel according to the error combination matrix.
Optionally, the method further includes acquiring real-time normal force of the wheel, generating a force distribution matrix according to the real-time traction force and the real-time normal force, and generating expected traction forces of different wheels according to the force distribution matrix.
The force control method of the wheeled robot of the invention has the same beneficial effects as the force control device of the wheeled robot, and is not repeated herein.
The invention also provides a wheeled robot, which comprises the force control device of the wheeled robot.
The invention also provides a wheeled robot, which comprises the force control device of the wheeled robot.
The beneficial effects of the wheeled robot of the present invention are the same as those of the force control method of the wheeled robot, and are not described herein again.
Drawings
Fig. 1 is a flowchart of a force control method of a wheeled robot according to an embodiment of the present invention;
fig. 2 is a top view of a force condition of a single wheel of the wheeled robot according to the embodiment of the invention;
fig. 3 is a schematic view of a stress situation of the wheeled robot according to the embodiment of the present invention;
fig. 4 is a block diagram of impedance control of the wheeled robot according to the embodiment of the present invention;
fig. 5 is a force control block diagram of a wheeled robot of an embodiment of the present invention;
fig. 6 is a block diagram of speed control of a wheeled robot according to an embodiment of the present invention;
fig. 7 is a force-velocity hybrid control block diagram of a wheeled robot according to an embodiment of the present invention;
FIG. 8 is a control block diagram of all wheels force control combined with a kinematic model according to an embodiment of the present invention;
fig. 9 is a system block diagram of a force control device of a wheeled robot of an embodiment of the present invention;
fig. 10 is a system block diagram of a force control device of a wheeled robot according to another embodiment of the present invention.
Description of reference numerals:
1-vehicle wheels; 2-a vehicle body; 12-desired wheel torque generation, 101-rotational speed acquisition, 102-desired rotational speed generation, 103-rotational speed error generation, 104-rotational speed switch matrix generation, 123-control law generation, 201-speed acquisition, 202-force distribution generation, 203-desired traction force generation, 301-force acquisition, 302-traction force error generation, 303-force switch matrix generation.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
In the description herein, references to the terms "an embodiment," "one embodiment," and "one implementation," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or implementation is included in at least one embodiment or example implementation of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or implementation. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or implementations.
An embodiment of the present invention provides a force control apparatus for a wheeled robot, as shown in fig. 9 and 10, including a rotational speed acquisition part 101 for acquiring real-time force of a wheel 1Rotational speed
Figure BDA0002611115920000051
A force acquisition part 301 for acquiring a real-time traction force of the wheel 1
Figure BDA0002611115920000052
A desired rotational speed generating part 3 for generating a desired speed v according to the vehicle body 2dGenerating a desired rotational speed of the wheel 1
Figure BDA0002611115920000053
A desired traction force generating part 203 for generating a desired traction force of the wheel 1
Figure BDA0002611115920000054
A desired wheel torque generation part 12 for generating a desired wheel torque in accordance with the desired rotation speed
Figure BDA0002611115920000055
And the desired tractive effort
Figure BDA0002611115920000056
Generating a desired torque T of said wheel 1d(ii) a A rotation speed error generating part 103 for generating a rotation speed error according to the real-time rotation speed
Figure BDA0002611115920000057
And the desired rotational speed
Figure BDA0002611115920000058
Generating a rotational speed error Tv(ii) a A traction error generating part 302 for generating a traction error according to the real-time traction
Figure BDA0002611115920000059
And the desired tractive effort
Figure BDA00026111159200000510
Generating a traction error Tf(ii) a A control law generating part 123 for generating a control law according to the traction force error TfThe error of the rotation speed TvAnd the desired torque TdA wheel force-speed hybrid control law T is generated, which is used for force tracking control or speed tracking control of the wheel 1.
As shown in fig. 9, the real-time rotation speed
Figure BDA00026111159200000511
Real-time acquisition by using a speed sensor, the real-time traction force
Figure BDA00026111159200000512
Acquired by post-acquisition processing with a force sensor, wherein the expected rotating speed is based on a kinematic model of the wheeled mobile robot
Figure BDA00026111159200000513
Comprises the following steps:
Figure BDA00026111159200000514
wherein, in combination with the slip ratio formula,
Figure BDA00026111159200000515
where S is the slip ratio, xe＝[xeze]TIs the end effector position, xr＝[xrzr]TIs the position in the state of rest in which,
Figure BDA00026111159200000516
a vector from the center of mass of the wheeled robot to the center of the ith wheel;
wherein the real-time rotation speed
Figure BDA0002611115920000061
And the desired rotational speed
Figure BDA0002611115920000062
For negative feedback regulation of the rotational speed of the wheel 1. That is to say thatAt said real-time rotational speed
Figure BDA0002611115920000063
Continuously correcting the real-time rotation speed as feedback information
Figure BDA0002611115920000064
Deviation from said desired speed
Figure BDA0002611115920000065
The error of the rotating speed is as follows:
Figure BDA0002611115920000066
here, the rotational speed error generating section is a rotational speed tracking PI controller, where KPv、KpfProportional and integral coefficients of the speed tracking PI controller are provided, respectively.
Wherein the real-time tractive effort
Figure BDA0002611115920000067
And the desired tractive effort
Figure BDA0002611115920000068
For negative feedback regulation of the desired traction of the wheel 1. That is, the control device uses the real-time tractive effort
Figure BDA0002611115920000069
Continuously correcting said real-time tractive effort as feedback information
Figure BDA00026111159200000610
And the desired tractive effort
Figure BDA00026111159200000611
Deviation between
Figure BDA00026111159200000612
The traction error is as follows:
Figure BDA00026111159200000613
here, the traction error generating section is a traction tracking PI controller, where KPf、KIfProportional and integral coefficients of the speed tracking PI controller are provided, respectively.
Based on the contact model and the wheel mechanics model, a nonlinear torque feedforward is obtained,
Figure BDA00026111159200000614
wherein,
Figure BDA00026111159200000615
and
Figure BDA00026111159200000616
is a diagonal coefficient matrix of a contact model for said wheel, FDPdAnd FNdIs a real-time traction force FDPAnd real-time normal force FNIs calculated from the expected value of (c).
Figure BDA00026111159200000617
Is a combination of intercept and fluctuation terms caused by the wheel pricks of all the driving wheels,
Figure BDA00026111159200000618
is a matrix of rotational inertia of the wheel.
Therefore, the real-time rotating speed and the real-time traction force of the wheel 1 are obtained, the expected torque of the wheel is generated according to the expected rotating speed and the expected traction force, the force-speed hybrid control law of the wheel is generated through the rotating speed error, the traction force error and the expected torque, the force or the speed of the wheel is tracked and controlled through the force-speed hybrid control law, the force-speed hybrid control of the wheel type robot is realized, and the control mode of the wheel type robot is convenient to switch between force control and speed control.
In the embodiment of the present invention, there are a plurality of pairs of the wheels 1, and the wheel force and speed hybrid control law is used to perform the rotational speed tracking control on one pair of the wheels 1 and perform the traction tracking control on the remaining wheels 1, so as to control the speed of the vehicle body 2, so that the interaction blocking acting force between different wheels 1 is minimized.
The invention respectively determines the force control law or the speed control law of a single wheel based on the single wheel, performs force control on one pair of wheels of the wheel type robot and performs speed control on other wheels, avoids performing force control or speed control on all wheels of the wheel type robot at the same time, and reduces mutual obstruction among different wheels. Particularly, on soft ground, the stress condition of the wheels changes, the force of the wheels is tracked in real time, the tracking error caused by pure speed tracking is prevented from becoming larger and larger, and the tracking error can be converged to zero by tracking the speeds of other wheels and correcting the track.
In an embodiment of the present invention, the force control apparatus of the wheeled robot further includes a rotational speed switch matrix generating section 104 for generating a rotational speed error combination matrix I-SDThe control law generating unit 123 further determines whether to perform the rotational speed tracking control on the wheel 1 according to the rotational speed error combination matrix; further comprises a force switch matrix generating part 303 for generating a traction force error combination matrix SDThe control law generating unit 123 further determines whether or not to perform traction force tracking control on the wheel 1 based on the traction force error combination matrix.
For example, where there are multiple pairs of wheels 1, and the selected pair of wheels is the ith and (i + 1) th wheels, a decoupled hybrid matrix can be designed as follows:
Figure BDA0002611115920000071
in the formula,
Figure BDA0002611115920000072
then, the control law of the wheel decoupling force/speed hybrid control is as follows:
T＝(I-SD)Tv+SDTf+Td
this arrangement is advantageous in that a rotation speed error combination matrix for wheel rotation speed tracking control and a traction error combination matrix for wheel force tracking control are generated by the arrangement of the rotation speed switch matrix generation section and the force switch matrix generation section 303, respectively, and rotation speed tracking control and traction force tracking control of the wheel are realized by two control systems, respectively.
In embodiments of the invention, force control and wheel speed control may also be coupled. Optionally, the control law generating unit 123 further performs a rotation speed tracking control or a traction tracking control on the wheel 1 according to the error combination matrix.
The coupling mixing matrix is defined as:
Figure BDA0002611115920000081
wherein S isCi∈(0，1)(i＝1，2，...，nw) Is the mixed relative coefficient of the ith round.
By controlling force and speed with SCIn combination, the control law of the wheel coupling force/speed hybrid control is expressed as follows:
T＝(I-SC)Tv+SCTf+Td
the advantage of such an arrangement is that by the arrangement of the error combining matrix, an error combining matrix for both the wheel speed tracking control and the wheel force tracking control is generated, while the speed tracking control or the traction tracking control of the wheel is realized.
In an embodiment of the present invention, the force acquisition part 301 is further configured to obtain a real-time normal force of the wheel 1, and further includes a force distribution generation part 202 configured to generate a force distribution matrix according to the real-time traction force and the real-time normal force, and the expected traction force generation part 203 is further configured to generate expected traction forces of different wheels 1 according to the force distribution matrix.
Here, the determining the force distribution condition a of the wheel includes:
obtaining a normal force of the wheel
Figure BDA0002611115920000082
The normal force is acquired by a force sensor;
according to the normal force
Figure BDA0002611115920000083
Determining a force distribution factor for the wheel
Figure BDA0002611115920000084
And
Figure BDA0002611115920000085
determining a force distribution condition of the wheel as a function of the force distribution factor and the normal force
Figure BDA0002611115920000091
Wherein,
Figure BDA0002611115920000092
is the normal force of the ith wheel,
Figure BDA0002611115920000093
is to be and
Figure BDA0002611115920000094
the unit vectors in the same direction are,
Figure BDA0002611115920000095
a vector from the center of mass of the wheeled robot to the center of the ith wheel;
thereby, according to the wheel type robot through setting the force distribution condition ADesired interaction force FdAnd determining the interaction force between different wheels and the vehicle body to optimize the interaction force between different wheels and the vehicle body, so as to reduce the obstruction between different wheels.
The force control device of the wheeled robot further comprises a speed acquisition part 201, which is used for acquiring the real-time speed of the vehicle body 2; the real-time velocity v and the desired velocity vdFor negative feedback regulation of the speed of the body 2. That is, the control device continuously corrects the real-time velocity v and the desired velocity v using the real-time velocity v as feedback informationdDeviation v betweend-v。
The present invention also provides a force control method of a wheeled robot, as shown in fig. 1, including:
step S1: acquiring the real-time rotating speed and the real-time traction of the wheel 1; generating a desired rotational speed of the wheel 1 in accordance with a desired speed of the vehicle body 2; obtaining a desired traction of the wheel 1;
step S2: generating a desired torque of the wheel 1 as a function of the desired speed and the desired traction;
step S3: generating a rotation speed error according to the real-time rotation speed and the expected rotation speed; generating a tractive effort error as a function of the real-time tractive effort and the desired tractive effort;
step S4: and generating a wheel force-speed hybrid control law according to the traction error, the rotating speed error and the expected torque, wherein the wheel force-speed hybrid control law is used for force-speed hybrid control of the wheel 1.
In the embodiment of the present invention, the method further includes acquiring a real-time normal force of the wheel 1, generating a force distribution matrix according to the real-time traction force and the real-time normal force, and generating expected traction forces of different wheels 1 according to the force distribution matrix.
In the embodiment of the present invention, there are multiple pairs of the wheels 1, and the method further includes performing rotational speed tracking control on one pair of the wheels 1 according to the wheel force and speed hybrid control law, and performing traction tracking control on the remaining wheels 1 to achieve speed control on the vehicle body 2, so as to minimize the mutual hindering acting force between different wheels 1.
In the embodiment of the invention, a rotating speed error combination matrix is determined, and whether the rotating speed tracking control is carried out on the wheel 1 is judged according to the rotating speed error combination matrix; and determining a traction error combination matrix, and judging whether to carry out traction tracking control on the wheel 1 according to the traction error combination matrix.
In the embodiment of the present invention, as shown in fig. 7 and 8, it is further comprised that an error combination matrix is determined, and the wheel 1 is subjected to the rotational speed tracking control or the traction tracking control according to the error combination matrix.
Desired interaction force F of the wheel and the wheeled robotdAcquiring the current speed v and the expected speed v of the wheeled robotdDetermining force distribution conditions A of different wheels; according to the current speed v and the expected speed vdAnd said force distribution condition A determines said desired interaction force Fd，
Figure BDA0002611115920000101
Wherein,
Figure BDA0002611115920000102
for acceleration, the acceleration may be obtained in real time; m'dFor desired inertia, KP、 KIRespectively PI controller coefficients, a being the force distribution condition of the wheel.
As shown in fig. 4, in the impedance control method, the driving torque of the wheeled robot is:
Figure BDA0002611115920000103
wherein G is gravity, V is centrifugal force, VdRefers to the desired speed of the wheeled mobile robot,
Figure BDA0002611115920000104
finger speed tracking error, M'd,DdAnd KdThe inertia M, the damping D and the rigidity K of the expected C are taken as driving moments IwIn order to be the moment of inertia,
Figure BDA0002611115920000105
in order to rotate the angle, the rotating shaft is rotated,
Rdit refers to the external force that is expected,
Figure BDA0002611115920000106
moment of inertia Iw＝diag{Iw1Iw2… Iwn}n×n；
Angle of rotation
Figure BDA0002611115920000107
Fig. 2 is a plan view of the force between the ith wheel and the vehicle body, as shown in fig. 2 and 3. Establishing a contact model for normal force and tangential driving force:
FN＝k(ze-zr)；
Figure BDA0002611115920000111
FNis the wheel normal force, k is the stiffness, mu is the coefficient of friction, FTIs the tangential driving force of the wheel,
Figure BDA0002611115920000112
is the equivalent mass of the robot, xe＝[xeze]TIs the end effector position, xr＝[xrzr]TIs the position in the rest state.
In connection with fig. 2 and 3, a wheel mechanics model is established for normal and tangential driving forces:
FN＝k′(z′e-zr)；
Figure BDA0002611115920000113
wherein,
Figure BDA0002611115920000114
Figure BDA0002611115920000115
from this, F can be determinedN＝k′(z′e-zr)；
Figure BDA0002611115920000116
Where k is stiffness, k' is equivalent stiffness, r, b are wheel radius and width, respectively, θ1And theta2Is the entry and exit angles, θmIs the maximum stress angle, theta is theta1To theta2Any angle therebetween. k is a radical ofcAnd
Figure BDA0002611115920000117
is a parameter of a characteristic of the terrain,
Figure BDA0002611115920000118
is the internal friction angle of the soil, N is the linear sinking coefficient of the soil,
Figure BDA0002611115920000119
is the wheel equivalent deflection, z'eIs the equivalent normal displacement coefficient, mu' is the equivalent friction coefficient, and K is the soil shear deformation modulus.
Combined slip ratio formula
Figure BDA00026111159200001110
Where S is the slip ratio.
Can determine
Figure BDA00026111159200001111
In connection with what is shown in fig. 3, it can be determined that:
Figure BDA00026111159200001112
Figure BDA00026111159200001113
wherein,
Figure BDA00026111159200001114
is and
Figure BDA00026111159200001115
unit vector of the same direction, Ti,mwi,Iwi,vi,μ′iRespectively, drive torque, mass, moment of inertia, linear velocity and friction angle,iFN,iFDP,iFT,
Figure BDA0002611115920000121
respectively the normal stress, the hook traction, the traction and the slip force of the ith wheel.
From this, a kinematic model of the wheeled robot can be determined:
Figure BDA0002611115920000122
wherein,
Figure BDA0002611115920000123
Figure BDA0002611115920000124
wherein,
Figure BDA0002611115920000125
linear and angular velocities of the wheel, respectively;
Figure BDA0002611115920000126
Figure BDA0002611115920000127
Figure BDA0002611115920000128
Figure BDA0002611115920000129
Figure BDA00026111159200001210
and can determine
Figure BDA00026111159200001211
Wherein,
Figure BDA00026111159200001212
Figure BDA00026111159200001213
Figure BDA00026111159200001214
v → 0, considering driving in soft ground; thus, it is possible to provide
Figure BDA0002611115920000131
Figure BDA0002611115920000132
Wherein, Fi＝iFDP-iFRActing force of a single wheel to the mass center of the vehicle body;
FR＝A(V+G+R′)；
Figure BDA0002611115920000133
Figure BDA0002611115920000134
Figure BDA0002611115920000135
Figure BDA0002611115920000136
Figure BDA0002611115920000137
Figure BDA0002611115920000138
in combination with a wheel-ground mechanics model,
Figure BDA0002611115920000139
wherein RC is a rolling resistance coefficient,
Figure BDA00026111159200001310
for robot equivalent mass, IwIs the moment of inertia.
In the case of a single wheel,
Figure BDA00026111159200001311
an impedance control law of a single wheel based on a driving torque of the wheeled robot is
Figure BDA00026111159200001312
Figure BDA00026111159200001313
Wherein,
Figure BDA00026111159200001314
error value representing angle of rotation, Fi dIs expected Fi，
Figure BDA00026111159200001316
Respectively representing desired moment of inertia, damping and stiffness.
In S1, as shown in fig. 5, a model for the desired interaction force control is established in advance:
Figure BDA0002611115920000141
wherein,
Figure BDA0002611115920000142
Figure BDA0002611115920000143
the current speed of the wheeled robot can be obtained in real time, the expected speed can be modified according to the real-time performance of the wheeled robot, and the expected speed can be determined according to the expected interaction force of the wheels.
Here, the determining the force distribution condition a of the wheel includes:
obtaining a normal force of the wheel
Figure BDA0002611115920000144
The normal force is acquired by a force sensor;
according to the normal force
Figure BDA0002611115920000145
Determining a force distribution factor for the wheel
Figure BDA0002611115920000146
And
Figure BDA0002611115920000147
determining a force distribution condition of the wheel as a function of the force distribution factor and the normal force
Figure BDA0002611115920000148
Wherein,
Figure BDA0002611115920000149
is the normal force of the ith wheel,
Figure BDA00026111159200001410
is to be and
Figure BDA00026111159200001411
the unit vectors in the same direction are,
Figure BDA00026111159200001412
a vector from the center of mass of the wheeled robot to the center of the ith wheel;
thereby, by setting the force distribution condition A, the desired interaction force F of the wheeled robot is obtaineddAnd determining the interaction force between different wheels and the vehicle body to optimize the interaction force between different wheels and the vehicle body, so as to reduce the obstruction between different wheels.
Based on the kinematic model of the wheeled mobile robot, the method can obtain
Figure BDA00026111159200001413
The impedance control function of the wheel can be obtained by the Lagrange equation:
Figure BDA0002611115920000151
for wheeled robots, the force control laws and kinematic models for all wheels can be combined, as shown below,
Figure BDA0002611115920000152
wherein,
Figure BDA0002611115920000153
Figure BDA0002611115920000154
Figure BDA0002611115920000155
Figure BDA0002611115920000156
Figure BDA0002611115920000157
Figure BDA0002611115920000158
wherein M' is the inertia of the wheeled robot, vdTo a desired speed, Iw dIn order to achieve the desired moment of inertia,
Figure BDA0002611115920000159
respectively representing desired moment of inertia, damping and stiffness,
Figure BDA00026111159200001510
is and
Figure BDA00026111159200001511
the unit vectors in the same direction are,
Figure BDA00026111159200001512
for traction of vehicle wheelsThe force is applied to the inner wall of the container,
Figure BDA00026111159200001513
is a vector from the centroid of the wheel robot to the ith wheel center.
When v approaches vdWhen the temperature of the water is higher than the set temperature,
Figure BDA00026111159200001514
the transfer function of all wheels after the combination of force control law and kinematic model and its block diagram are shown in fig. 8;
Figure BDA00026111159200001515
in an embodiment of the present invention, as shown in fig. 5, the determining of the force control law of the wheeled robot includes:
determining angular acceleration of the wheel
Figure BDA00026111159200001516
And rolling resistanceiFRDetermining the current interaction force F of the wheel and the vehicle bodyi(ii) a Determining the current interaction force F of the wheel and the vehicle bodyiThe method comprises the following steps:
obtaining traction F of said wheelDPDetermining the resistance of the wheel to the bodyiFR；
According to the traction force F of the wheelDPAnd the resistance of the wheel to the vehicle bodyiFRDetermining the current interaction force Fi＝iFDP-iFR；
According to the current interaction force FiThe normal force, the angular acceleration
Figure BDA0002611115920000161
And the rolling resistanceiFRDetermining a current torque T of the wheeli；
Wherein,
Figure BDA0002611115920000162
determining force control law of the wheeled robot according to the current torque based on a PI controller
Figure BDA0002611115920000163
Here, as shown in fig. 6, the desired trajectory q of the wheeldThe determination of (1) comprises: obtaining a current traction force F of the wheelDPAnd a reference trajectory q of said wheelr(ii) a According to said desired interaction force, current traction force FDPAnd a reference trajectory q of said wheelrDetermining a desired trajectory q of said wheeld。
The desired moment of inertia of the wheel is
Figure BDA0002611115920000164
The desired damping of the wheel is
Figure BDA0002611115920000165
The desired stiffness of the wheel is
Figure BDA0002611115920000166
Figure BDA0002611115920000167
Wherein,
Figure BDA0002611115920000168
by laplace variation, one can obtain:
Figure BDA0002611115920000169
wherein,
Figure BDA00026111159200001610
j is the Jacobian matrix of the current slip rate s (t), xrAnd (t) is a reference track of the wheeled robot.
Derived from unexpected variations in wheel slip due to discordance between wheels
Figure BDA00026111159200001611
It may not be reasonable to track such
Figure BDA00026111159200001612
The tracking precision of the wheeled robot is reduced. If the desired force is tracked, however, the mismatch can be eliminated, ideally,
Figure BDA00026111159200001613
based on the contact model and the wheel mechanics model, a nonlinear torque feedforward is obtained,
Figure BDA0002611115920000171
wherein,
Figure BDA0002611115920000172
and
Figure BDA0002611115920000173
is a diagonal coefficient matrix of a contact model for said wheel, FDPdAnd FNdIs FDPAnd FNIs calculated from the expected value of (c).
Figure BDA0002611115920000174
Is a combination of intercept and fluctuation terms caused by the wheel pricks of all the driving wheels,
Figure BDA0002611115920000175
is a matrix of rotational inertia of the wheel.
Reference trajectory q of said wheelrCan be encoded byAnd the device acquires the expected rotating speed of the wheel in real time and tracks the expected rotating speed of the wheel through a PI controller.
The invention also provides a wheeled robot, which comprises the force control device of the wheeled robot. The beneficial effects of the wheeled robot of the present invention are the same as those of the force control method of the wheeled robot, and are not described herein again.
Although the present disclosure has been described above, the scope of the present disclosure is not limited thereto. Various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present disclosure, and these changes and modifications are intended to be within the scope of the present disclosure.

Claims (14)

1. A force control device of a wheeled robot is characterized by comprising a rotating speed acquisition part (101) for acquiring the real-time rotating speed of a wheel (1); a force acquisition unit (301) for acquiring a real-time traction force of the wheel (1); a desired rotation speed generation unit (3) for generating a desired rotation speed of the wheel (1) from a desired speed of a vehicle body (2); a desired traction force generation unit (203) for generating a desired traction force of the wheel (1); a desired wheel torque generation section (12) for generating a desired torque of the wheel (1) in accordance with the desired rotational speed and the desired traction force; a rotational speed error generation unit (103) for generating a rotational speed error from the real-time rotational speed and the desired rotational speed; a tractive effort error generation unit (302) for generating a tractive effort error from the real-time tractive effort and the desired tractive effort; and a control law generation unit (123) for generating a wheel-force-and-speed hybrid control law for force tracking control or speed tracking control of the wheel (1) on the basis of the traction force error, the rotational speed error, and the desired torque.
2. A force control arrangement of a wheeled robot according to claim 1, characterized in that said real time rotational speed and said desired rotational speed are used for negative feedback regulation of the rotational speed of the wheels (1).
3. A force control arrangement of a wheeled robot according to claim 1, characterized in that said real time traction force and said desired traction force are used for negative feedback regulation of the desired traction force of the wheels (1).
4. Force control arrangement of a wheeled robot according to claim 1, characterised in that there are several pairs of wheels (1), and that the wheel force and speed hybrid control law is used for speed tracking control of one pair of wheels (1) and traction tracking control of the remaining wheels (1) to achieve speed control of the body (2) such that the mutually hindering forces between different wheels (1) are minimized.
5. The force control device for a wheeled robot according to claim 4, further comprising a rotational speed switch matrix generation unit (104) for generating a rotational speed error combination matrix, wherein the control law generation unit (123) further determines whether or not to perform rotational speed tracking control on the wheel (1) based on the rotational speed error combination matrix; the traction control device further comprises a force switch matrix generation unit (303) for generating a traction error combination matrix, and the control law generation unit (123) determines whether to perform traction tracking control on the wheel (1) according to the traction error combination matrix.
6. The force control device for a wheeled robot according to claim 4, further comprising a switch matrix generation unit (23) for generating an error combination matrix, wherein the control law generation unit (123) further performs rotational speed tracking control or traction tracking control on the wheel (1) based on the error combination matrix.
7. A force control device of a wheeled robot according to claim 4, characterized by further comprising a speed acquisition part (201) for acquiring a real-time speed of the vehicle body (2); the real-time speed and the desired speed are used for negative feedback adjustment of the speed of the vehicle body (2).
8. The force control device of a wheeled robot according to claim 7, characterized in that said force acquisition part (301) is further adapted to obtain real-time normal forces of said wheels (1), further comprising a force distribution generation part (202) adapted to generate a force distribution matrix from said real-time tractive forces and said real-time normal forces, said desired tractive forces generation part (203) being further adapted to generate desired tractive forces of different said wheels (1) from said force distribution matrix.
9. A force control method of a wheeled robot, characterized by comprising:
acquiring the real-time rotating speed and the real-time traction of the wheel (1); -generating a desired rotational speed of the wheel (1) from a desired speed of the vehicle body (2); -acquiring a desired traction of the wheel (1);
generating a desired torque of the wheel (1) as a function of the desired rotational speed and the desired traction;
generating a rotation speed error according to the real-time rotation speed and the expected rotation speed; generating a tractive effort error as a function of the real-time tractive effort and the desired tractive effort;
and generating a wheel force-speed hybrid control law according to the traction error, the rotating speed error and the expected torque, wherein the wheel force-speed hybrid control law is used for force-speed hybrid control of the wheel (1).
10. A method for controlling force of a wheeled robot according to claim 9, wherein there are a plurality of pairs of said wheels (1), further comprising performing a rotational speed tracking control on one of said pairs of wheels (1) and performing a traction tracking control on the remaining wheels (1) according to a hybrid control law of the wheel force and the wheel speed to control the speed of said vehicle body (2) so as to minimize the mutual interference force between different wheels (1).
11. The force control method of a wheeled robot according to claim 10, further comprising determining a rotation speed error combination matrix, and determining whether or not to perform rotation speed tracking control on the wheel (1) based on the rotation speed error combination matrix; and determining a traction error combination matrix, and judging whether to carry out traction tracking control on the wheel (1) according to the traction error combination matrix.
12. A method of force control of a wheeled robot according to claim 10, further comprising determining an error combination matrix, according to which the wheel (1) is speed tracking controlled or traction tracking controlled.
13. A method for force control of a wheeled robot according to claim 10, further comprising obtaining real time normal forces of the wheels (1), generating a force distribution matrix from said real time tractive forces and said real time normal forces, generating desired tractive forces of different wheels (1) from said force distribution matrix.
14. A wheeled robot comprising a force control device of a wheeled robot according to any one of claims 1-8.
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