CN110525534A - A kind of small vehicle chassis structure and its control method using complicated landform - Google Patents

A kind of small vehicle chassis structure and its control method using complicated landform Download PDF

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Publication number
CN110525534A
CN110525534A CN201910920431.2A CN201910920431A CN110525534A CN 110525534 A CN110525534 A CN 110525534A CN 201910920431 A CN201910920431 A CN 201910920431A CN 110525534 A CN110525534 A CN 110525534A
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China
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vehicle
wheel
planet
mecanum
torque
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洪日
闵昭翔
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Jilin University
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Jilin University
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Priority to CN201910920431.2A priority Critical patent/CN110525534A/en
Publication of CN110525534A publication Critical patent/CN110525534A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
    • B60B19/00—Wheels not otherwise provided for or having characteristics specified in one of the subgroups of this group
    • B60B19/12—Roller-type wheels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D57/00—Vehicles characterised by having other propulsion or other ground- engaging means than wheels or endless track, alone or in addition to wheels or endless track
    • B62D57/02—Vehicles characterised by having other propulsion or other ground- engaging means than wheels or endless track, alone or in addition to wheels or endless track with ground-engaging propulsion means, e.g. walking members
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60B—VEHICLE WHEELS; CASTORS; AXLES FOR WHEELS OR CASTORS; INCREASING WHEEL ADHESION
    • B60B2900/00—Purpose of invention
    • B60B2900/50—Improvement of
    • B60B2900/551—Handling of obstacles or difficult terrains

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Retarders (AREA)

Abstract

The present invention discloses a kind of small vehicle chassis structure using complicated landform, comprising: chassis；Multiple Mecanum wheel groups, symmetrical and rotatable support are arranged in the chassis two sides, and the Mecanum wheel group includes: planet carrier；Sun gear is arranged at planet carrier side center；Multiple planetary gears, the planet carrier for being uniformly arranged on the sun gear circumferential direction is ipsilateral, and engages with the sun gear；Multiple first sprocket wheels, setting are corresponded and are coaxially disposed in the planet carrier other side, and with the planetary gear；Multiple second sprocket wheels are separately positioned on the planet carrier other side between first sprocket wheel；Chain is sequentially connected first sprocket wheel and second sprocket wheel；Multiple Mecanum wheels, setting are corresponded and are coaxially disposed in the planet carrier other side, and with second sprocket wheel；Power mechanism, output end and the sun gear are coaxially connected, for driving the sun gear to rotate.

Description

Small-sized vehicle chassis structure applying complex terrain and control method thereof
Technical Field
The invention relates to the technical field of vehicle chassis structures, in particular to a small vehicle chassis structure applying complex terrains and a control method thereof.
Background
In recent years, in many fields such as disaster relief, counter terrorism and logistics, ground robots with good performance are required to perform tasks such as detection, investigation and transportation. The robot is small, exquisite and flexible, good in trafficability characteristic, capable of entering and exiting various complex terrain environments, capable of achieving different functions by carrying different loading platforms and popular in the market. The conventional wheel-driven or crawler-type driven small vehicle chassis is still applied to the market at present, but the chassis does not have omnidirectional moving capability and is still inconvenient to use in some narrow environments. In addition, the chassis is small, so that the obstacle crossing capability of the chassis is tested when the chassis travels in environments such as ruins, stairs and the like.
Disclosure of Invention
The invention designs and develops a chassis structure of a small vehicle applying complex terrains, a plurality of Mecanum wheel sets are symmetrically and rotatably supported on two sides of the chassis, and a two-degree-of-freedom planetary gear train is arranged in the Mecanum wheel sets, so that the chassis can move in various postures on the ground, and the trafficability of the vehicle in a narrow space and the ability of crossing obstacles are improved.
The invention designs and develops a control method of a chassis structure of a small vehicle applying complex terrains, which can control the running state of each Mecanum wheel set according to the running road surface condition.
The invention can also control the torque and the distribution coefficient of the power mechanisms on the two sides of the front and rear axles according to the running road surface condition and the running state of the vehicle, thereby improving the running stability of the vehicle.
The technical scheme provided by the invention is as follows:
a small vehicle chassis structure using a complex terrain, comprising:
a chassis; and
a plurality of Mecanum wheel sets symmetrically and rotatably supported on both sides of the chassis, the Mecanum wheel sets comprising:
a planet carrier;
a sun gear which is arranged at the center of one side of the planet carrier and can rotate along the axial direction of the sun gear;
the planet gears are uniformly arranged in the circumferential direction of the sun gear and are meshed with the sun gear, and the planet gears can revolve around the sun gear in the axial direction and drive the planet carrier to rotate and can also rotate around the self axial direction;
the first chain wheels are arranged on the other side of the planet carrier, correspond to the planet wheels one by one and are coaxially arranged, and the first chain wheels and the corresponding planet wheels synchronously move;
the second chain wheels are respectively arranged on the other side of the planet carrier between the first chain wheels and can rotate around the axial direction of the second chain wheels;
a chain which is connected with the first chain wheel and the second chain wheel in sequence and is in a tensioning state;
the first chain wheel and the second chain wheel are respectively positioned on two sides of the chain;
the Mecanum wheels are arranged on the other side of the planet carrier, correspond to the second chain wheels one by one and are coaxially arranged, and the Mecanum wheels and the corresponding second chain wheels synchronously move;
and the output end of the power mechanism is coaxially and fixedly connected with the sun wheel and is used for driving the sun wheel to rotate.
Preferably, the carrier includes:
a first frame plate;
the second frame plate is parallel to the first frame plate and arranged at intervals;
the first frame plate and the second frame plate are consistent in structure and are both triangular plate-shaped structures; and
sun gear and planet wheel set up first frame plate lateral surface, first sprocket, second sprocket and chain setting are in first frame plate with between the second frame plate, mecanum wheel sets up the second frame plate outside.
Preferably, the method further comprises the following steps:
the sun wheel shaft fixedly penetrates through the sun wheel, one end of the sun wheel shaft is rotatably arranged in the center of the outer side face of the first frame plate, and the other end of the sun wheel shaft is fixedly connected with the output end of the power mechanism;
the planet shafts can rotatably penetrate through the first carrier plate and the second carrier plate and correspond to the planet wheels one by one;
the planet wheels are coaxially and fixedly arranged on the planet shaft positioned on the outer side of the first frame plate, and the first chain wheel is coaxially and fixedly arranged on the planet shaft positioned between the first frame plate and the second frame plate;
the chain wheel shafts can rotatably penetrate through the first frame plate and the second frame plate and correspond to the second chain wheels one by one;
the second chain wheel is coaxially and fixedly arranged on the chain wheel shaft between the first frame plate and the second frame plate, and the Mecanum wheel is fixedly arranged on the chain wheel shaft on the outer side of the second frame plate.
Preferably, the power mechanism further includes:
the bearing seats are arranged on the outer side of the first frame plate at intervals, and the centers of the bearing seats can rotatably penetrate through the output end of the power mechanism;
wherein the sun gear and the planet gear are arranged between the first frame plate and the bearing seat, and the planet shaft can rotate the bearing seat.
Preferably, the vehicle further comprises a slope angle sensor arranged on the chassis and used for detecting the gradient of the running bottom surface of the vehicle.
Preferably, the number of the Mecanum wheel sets is 4, and the Mecanum wheel sets are symmetrically and rotatably supported on the chassis; each Mecanum wheel set is provided with 3 Mecanum wheels and encloses an equilateral triangle.
A method of controlling a chassis structure of a small vehicle utilizing complex terrain, comprising:
when the vehicle runs on the flat ground without obstacles, the planet wheels only rotate around the self axial direction, and the first chain wheel and the second chain wheel drive the Mecanum wheel to rotate to drive the vehicle to run;
when the vehicle runs in an obstacle, the planet wheel axially rotates and also axially revolves around the sun wheel, the planet carrier is driven to drive the Mecanum wheel set to rotate, and the vehicle is driven to move forwards and cross the obstacle;
wherein, when the vehicle is traveling, only 2 and only 2 of the Mecanum wheel sets are simultaneously grounded.
Preferably, when the vehicle runs at a constant speed without obstacles on the flat ground, the torque of the power mechanism controlling the two sides of the front and rear shafts satisfies the following conditions:
wherein,is the inclination angle of the vehicle in the horizontal direction, and H is the height of the mass center when the vehicle is horizontally placed; l is the distance between the front axle and the rear axle of the vehicle; b is the distance between the center of mass and the axis of the rear axle in the horizontal direction when the rear axle is horizontally placed; g is the total gravity of the vehicle during operation, MA1、MA2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the front shaft are respectively; mB1、MB2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the rear shaft are respectively; r iscThe radius of gyration of the Mecanum wheel axis around the planet wheel train center when the planet wheel train revolves;
and controlling the torque distribution coefficient s of the front and rear shafts to satisfy:
wherein the maximum climbing capability of the vehicleSatisfies the following conditions:
wherein igIs the planetary gear set transmission ratio; i.e. isThe transmission ratio of the chain wheel set is set; d is the Mecanum wheel diameter.
Preferably, when the vehicle starts or runs with acceleration without obstacles, the torque of the power mechanism controlling both sides of the front and rear shafts satisfies:
wherein L is the distance between the front axle and the rear axle of the vehicle; g is the total gravity of the vehicle during operation, MA1、MA2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the front shaft are respectively; mB1、MB2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the rear shaft are respectively; r iscThe radius of rotation of a Mecanum wheel axis around the center of the planetary gear train during the revolution of the planetary gear train, d is the diameter of the Mecanum wheel, igIs the planetary gear set transmission ratio; i.e. isIs the transmission ratio of the chain wheel set, and H is the height of the mass center when the vehicle is horizontally placed;
and controlling the torque distribution coefficient s of the front and rear shafts to satisfy:
and controlling the acceleration a of the vehicle to satisfy:
wherein m is0Is the total mass of the vehicle when in operation.
Preferably, when the vehicle runs at a constant speed, starts or accelerates on a flat ground, the rotating speed of the Mecanum wheel set is controlled to meet the following conditions:
ωi＝ωi1＝ωi2＝ωi3，i＝1，2，3，4；
wherein, ω is1Is the rotational speed, omega, of the left front Mecanum wheel set2For the speed of rotation, omega, of the right front Mecanum wheel set3Is the rotation speed, omega, of the left rear Mecanum wheel set4The rotation speed of the rear right Mecanum wheel group; r is the grounding radius of the Mecanum wheel; y is half of the wheelbase; x is half of the distance between the grounding points of the left and right wheels, omegaiFor the speed of the ith Mecanum wheel set, ωi1For the speed of the first Mecanum wheel in the ith Mecanum wheel set，ωi2For the speed, ω, of the second Mecanum wheel of the ith Mecanum wheel seti3For the speed of rotation of the third Mecanum wheel of the ith Mecanum wheel set, VXFor the transverse running speed of the vehicle, VYAs the longitudinal running speed, ω, of the vehicleoIs the vehicle spin angular velocity.
Preferably, when the vehicle runs in an obstacle, the torque of the power mechanism controlling the two sides of the front and rear shafts satisfies the following conditions:
wherein,is the inclination angle of the vehicle in the horizontal direction, and H is the height of the mass center when the vehicle is horizontally placed; l is the distance between the front axle and the rear axle of the vehicle; b is the distance between the center of mass and the axis of the rear axle in the horizontal direction when the rear axle is horizontally placed; g is the total gravity of the vehicle during operation, MA1、MA2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the front shaft are respectively; mB1、MB2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the rear shaft are respectively; r iscThe radius of gyration of the Mecanum wheel axis around the planet wheel train center when the planet wheel train revolves;
and controlling the torque distribution coefficient s of the front and rear shafts to satisfy:
the invention has the following beneficial effects:
(1) the chassis structure of the small vehicle applied to the complex terrain, which is designed and developed by the invention, is symmetrically and rotatably supported on the two sides of the chassis and is provided with a plurality of Mecanum wheel sets, so that the chassis can move on the ground in various postures, including front-back translation, self-rotation, transverse movement, diagonal movement, turning and the like, the trafficability of the vehicle in a narrow space and the capability of crossing obstacles are improved, and the vehicle can move in complex environments such as good roads, stairs, ruins and the like.
(2) The vehicle chassis is connected with the Mecanum wheel set by carrying the two-degree-of-freedom planetary gear train, normal running on flat ground is realized by the mechanical characteristics of the planetary gear train, the function of automatically identifying and supporting the chassis to cross obstacles when the vehicle chassis encounters an obstacle, and a redundant sensor and a control system are not needed. Compared with the traditional ground robot chassis, the invention improves the trafficability in a narrow space and the ability of crossing over obstacles.
(3) The control method of the chassis structure of the small vehicle applying the complex terrain, which is designed and developed by the invention, can control the running state of each Mecanum wheel set according to the running road surface condition. The torque and the distribution coefficient of the power mechanisms on both sides of the front and rear axles can be controlled according to the running road surface condition and the running state of the vehicle, so that the running stability of the vehicle is improved.
Drawings
Fig. 1 is a schematic structural view of a chassis structure of a small vehicle using a complex terrain according to the present invention.
Fig. 2 is a schematic structural diagram of a mecanum wheel set according to the present invention.
Fig. 3 is a schematic diagram of the arrangement structure of the sun wheel and the planet wheel.
Fig. 4 is a schematic view of the arrangement of the sprocket set according to the present invention.
Fig. 5 is a schematic view of the working state of the vehicle obstacle crossing according to the present invention.
Fig. 6 is a schematic diagram of a motion analysis coordinate system of a chassis mecanum wheel according to the present invention.
Fig. 7 is a schematic diagram of a motion analysis coordinate system of a chassis mecanum wheel according to the present invention.
Detailed Description
The present invention is further described in detail below with reference to the attached drawings so that those skilled in the art can implement the invention by referring to the description text.
As shown in fig. 1, the present invention provides a chassis structure of a small vehicle using a complex terrain, in which four power mechanisms 110 are provided in a vehicle chassis 100, and the power mechanisms are selected as servo motors for precise control of the posture of the vehicle body due to the use of mecanum wheels. A reduction box with a proper transmission ratio is integrated on the motor. The power adopts lithium cell group, is fixed in on the frame. A toe sensor is further provided on the chassis 100 for detecting the gradient of the road surface on which the vehicle is traveling.
In the vehicle chassis 100, a power transmission route is a motor-planetary gear train-mecanum wheel. 4 groups of motors 110 and planetary gear trains 120 are provided; each set of planetary gear trains 120 is connected to 3 mecanum wheels 130 (collectively referred to as mecanum wheel sets), the three mecanum wheels 130 enclose an equilateral triangle, and there are 12 mecanum wheels 130 on the chassis 100. The planetary gear train 120 includes a planetary gear set and a sprocket set, which are respectively disposed on two adjacent and parallel planes, and a carrier 140 is disposed between the two planes.
As shown in fig. 2, the planet carrier 140 includes a first frame plate 141 and a second frame plate 142 spaced apart from and parallel to each other, and both of the first frame plate and the second frame plate have the same structure and are triangular plate-shaped structures.
The planetary gear train 120 includes a sun gear 121 rotatably disposed at the outer center of the first frame plate 141 through a sun gear shaft 122, the sun gear shaft 122 fixedly penetrates the center of the sun gear 121, and one end of the sun gear shaft 122 is rotatably disposed at the outer center of the first frame plate 141, a plurality of planetary gears 123 are uniformly disposed at the same side of the first frame plate 141 in the circumferential direction of the sun gear 121 through planetary shafts 124 and engaged with the sun gear 121, and the planetary gears 123 can revolve around the sun gear 121 in the axial direction and drive the planetary carrier 140 to rotate, and also can rotate around the axial direction. The planet shaft 124 rotatably penetrates the first carrier plate 141 and the second carrier plate 142, and the planet wheels 123 are coaxially and fixedly arranged on the planet shaft 124 outside the first carrier plate 141, as shown in fig. 3.
The planetary gear train 120 further includes a sprocket set, as shown in fig. 4, specifically including a plurality of first sprockets 125, which are disposed between the first frame plate 141 and the second frame plate 142, and are in one-to-one correspondence with the planetary gears 123 and coaxially fixed on the planetary shafts 124 between the first frame plate 141 and the second frame plate 142, wherein the first sprockets 125 and the corresponding planetary gears 123 move synchronously; and a plurality of second sprockets 126 respectively disposed on the other side of the planet carrier 140 (i.e., between the first and second carrier plates 141 and 142) between the first sprockets 125 via the sprocket shafts 127 and capable of rotating axially about themselves. The sprocket shaft 127 rotatably passes through the first frame plate 141 and the second frame plate 142 and corresponds to the second sprockets 126 one by one, the second sprockets 136 are coaxially and fixedly arranged on the sprocket shaft 127 between the first frame plate 141 and the second frame plate 142, and the mecanum wheel 130 is fixedly arranged on the sprocket shaft 127 on the outer side of the second frame plate 142 and moves synchronously with the corresponding second sprockets 126. A chain 128, which in turn connects the first sprocket 125 and the second sprocket 126 and is in tension, with the first sprocket 125 and the second sprocket 126 on either side of the chain 128.
An output shaft 111 of the servo motor 110 is splined to a sun gear shaft 122 for driving the sun gear 121 to rotate. In this embodiment, the device further comprises a bearing seat 129 which is arranged outside the first frame plate 141 at intervals, and the center of the bearing seat can rotatably penetrate through the output shaft of the servo motor 110, and the output shaft can freely rotate in the bearing seat 129; the planet shaft 124 is rotatably inserted through the bearing housing 129 at an end thereof located outside the first carrier plate 141. The sun gear 121 and planet gears 123 are arranged between the first carrier plate 141 and the bearing housing 129.
Planetary gear train 120 mounted on the chassis of the vehicle has two degrees of freedom in which planetary gear 123 rotates and planetary gear 123 revolves during driving. During driving, power is input to the sun gear 121 from the output shaft of the motor reduction box, the sun gear 121 is meshed with the planet gear 123, and the two degrees of freedom of rotation or revolution of the planet gear 121 are not rigidly constrained. The revolution of the planet wheels 123 drives the planet carrier 140 to rotate, and simultaneously drives the three peripheral Mecanum wheels 130 to revolve around the central axis of the planet wheel train 120; the rotation of the planet wheel 123 drives a coaxial first chain wheel 125, and drives three second chain wheels 126 to rotate through a chain 128, and the second chain wheels 126 drive a mecanum wheel winding wheel 130 connected with the second chain wheels to rotate around the axes thereof through a chain wheel shaft 127.
Therefore, when the vehicle runs on the flat ground, the output torque of the motor is lower, the revolution torque of the planet wheels is smaller than the constraint caused by the gravity of the vehicle body, so that the planet wheels cannot revolve, the rotation of the planet wheels drives the Mecanum wheels to rotate through chain transmission, and the vehicle is driven to run forwards. When the vehicle meets an obstacle, the output torque of the motor is increased, the revolution torque of the planet wheels is also increased, and when the output torque of the motor is larger than the constraint caused by the gravity of the vehicle, the planet gears start to revolve, and simultaneously drive the planet carrier and the Mecanum wheel to revolve, so that the vehicle is driven to move forward and cross the obstacle.
Mecanum wheel 130 is comprised of spokes and a plurality of small rollers fixed to the outer periphery, with the angle between the wheel and the rollers being 45. Each wheel has three degrees of freedom, one is rotational about the wheel axis, the second is rotational about the roller axis, and the third is rotational about the contact point of the wheel with the ground. The wheel is driven by the chain wheel shaft of the second chain wheel in the planetary gear train, so the other two degrees of freedom move freely. Each group of planetary gear trains is provided with three Mecanum wheels with the same option, and the three wheels are fixedly connected by second chain wheels which are respectively connected with each other through chains. When the planetary gear train is used on the flat ground, two Mecanum wheels of each group of planetary gear train are grounded, and the other one is suspended. Therefore, eight traveling wheels are grounded when the vehicle travels on the flat ground. The Mecanum wheels on the two adjacent planetary gear trains have different rotation directions. Due to the unique structure of the Mecanum wheels, the moving mechanism can move in all directions in a good road environment and can randomly switch the moving states of straight movement, transverse movement, oblique movement and the like. When the bicycle runs on a road surface with a poor adhesion coefficient such as a mud land, a sand land and the like, the plurality of grounded rollers on each Mecanum wheel form deep tire lines, so that the adhesion coefficient can be increased.
The chassis structure of the small vehicle applied to the complex terrain, which is designed and developed by the invention, is symmetrically and rotatably supported on the two sides of the chassis and is provided with a plurality of Mecanum wheel sets, so that the chassis can move on the ground in various postures, including front-back translation, self-rotation, transverse movement, diagonal movement, turning and the like, the trafficability of the vehicle in a narrow space and the capability of crossing obstacles are improved, and the vehicle can move in complex environments such as good roads, stairs, ruins and the like. The vehicle chassis is connected with the Mecanum wheel set by carrying the two-degree-of-freedom planetary gear train, normal running on flat ground is realized by the mechanical characteristics of the planetary gear train, the function of automatically identifying and supporting the chassis to cross obstacles when the vehicle chassis encounters an obstacle, and a redundant sensor and a control system are not needed. Compared with the traditional ground robot chassis, the invention improves the trafficability in a narrow space and the ability of crossing over obstacles.
The invention also provides a control method of a chassis structure of a small vehicle applying complex terrain, which comprises the following steps:
(1) when the vehicle travels on the flat ground without obstacles, the planet wheel only rotates around the self axial direction, and drives the Mecanum wheel to rotate through the first chain wheel and the second chain wheel so as to drive the vehicle to travel;
(2) when the vehicle runs in an obstacle (as shown in fig. 5), the planet wheels revolve around the sun wheel in the axial direction while rotating around the self axis, the planet carrier is driven to drive the mecanum wheel set to rotate, and the vehicle is driven to move forward and cross the obstacle;
wherein, when the vehicle is traveling, only 2 and only 2 of the Mecanum wheel sets are simultaneously grounded.
When the vehicle chassis moves, the planetary gear train has two degrees of freedom of rotation and revolution simultaneously, wherein the degree of freedom of rotation is unconstrained, and the degree of freedom of revolution is constrained by the reaction force between the gravity of the vehicle and the ground. When the revolution torque of the chassis planetary gear train is larger than the moment generated by the reaction force between the gravity of the vehicle and the ground, the planetary gear train starts to revolve.
When the vehicle needs to run on flat ground, in order to ensure smooth running, the revolution freedom degree of the planetary gear train needs to be restricted, and the Mecanum wheel is driven to run forward only by the autorotation of the planetary gear. Therefore, when the vehicle travels on the flat ground, the output torques of the four motors of the vehicle need to be limited (controlled) so as to prevent the revolution torque of the planetary gear train from being too large due to the too large output torque of the individual motor, and the vehicle can run in a bumpy manner corresponding to the revolution of the planetary gear train.
In order to ensure the use safety, when the vehicle travels on a rugged landform downhill, the front axle motor is driven, and the rear axle motor is slightly braked, so that a backward turning moment is provided for the vehicle, and the vehicle is prevented from turning forward.
(1.1) when the vehicle travels at a constant speed and flat ground without obstacles, assuming that the ground adhesion coefficient is good and no sliding friction occurs between the Mecanum wheels and the ground, the speed v when the vehicle travels on the flat ground is:
wherein: n is the rotating speed of the output shaft of the motor; i.e. igIs the planetary gear set transmission ratio; i.e. isThe transmission ratio of the chain wheel set is set; d is the Mecanum wheel diameter.
Since the output torque of the motor is limited (controlled) when the vehicle travels on a flat ground, and the output torque of the motor on a good road surface mainly depends on the ground gradient and the vehicle acceleration (the constant-speed running acceleration is 0), the maximum climbing capability of the vehicle under the condition that the planetary gear train does not revolve needs to be researched, and the cooperative working mode of the front and rear shaft motors is needed to meet the maximum climbing gradient.
On a slope, the influence of the inclination degree of the road surface on the road surface pressure of the front axle and the rear axle of the vehicle is as follows:
wherein:for the inclination of the vehicle in the horizontal direction, FANormal pressure of the ground to the front axle; fBNormal ground to rear axle pressure; h is the height of the mass center when the vehicle is horizontally placed; l is the distance between the front axle and the rear axle of the vehicle; b is the distance between the center of mass and the axis of the rear axle in the horizontal direction when the rear axle is horizontally placed; g is the total gravity of the vehicle when in operation.
After simplified finishing, the following can be obtained:
when the front-rear axis planetary gear train generates a critical value during revolution, the relationship between the motor torque and the normal pressure of the corresponding axis is as follows:
wherein: mA1max、MA2maxThe motors at the left and right sides of the front shaft start revolution at the planetary gear trainCritical torque at time; mB1max、MB2maxCritical torque of the motors at the left side and the right side of the rear shaft when the planetary gear train starts revolution respectively; r iscWhen the planetary gear train revolves, the axis of the Mecanum wheel revolves around the center of the planetary gear train by a radius.
Thus, if the inclination of the vehicle in the horizontal direction is knownThe maximum torque which can be sent out by the front and rear shaft motors when the planetary gear train does not revolve can be calculated.
When in useWhen the angle reaches the maximum value that the vehicle can climb, i.e. whenWhen the vehicle driving force is equal to the gliding force of the delaying slope:
after finishing, the method can be obtained:
in summary,may represent the maximum climbing capability of the vehicle. In order to fully utilize the driving force of the vehicle and increase the driving force as much as possible on the premise of avoiding the revolution of the planetary gear train, the front and rear motors need to be cooperatively controlled, the optimal torque distribution coefficient s of the front and rear motors is taken as a control target, and the torque output of the front and rear motors is controlled by a parameter s. The calculation process of s is as follows:
therefore, when the vehicle runs on the flat ground at a constant speed without obstacles, the torque of the power mechanism (servo motor) on both sides of the front and rear shafts should be controlled to satisfy:
wherein M isA1、MA2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the front shaft are respectively; mB1、MB2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the rear shaft are respectively;
and controlling the torque distribution coefficient s of the front and rear shafts to satisfy:
(1.2) when the vehicle accelerates on the flat ground without obstacles, the output torque of the motor is also related to the acceleration of the vehicle, and in order to avoid the planetary gear train from generating revolution and bump, the maximum acceleration of the vehicle is limited, and the torque of a front shaft motor and a rear shaft motor when the vehicle accelerates is controlled.
When the vehicle accelerates forwards at an acceleration a, the normal pressure relation between the front and rear axes and the ground is as follows:
wherein: m is0Is the total mass of the vehicle when in operation.
The relationship between the acceleration a and the motor drive torque is:
when the front and rear axle planetary carriers are in a limiting state before revolution, the relationship between the torque of the motor and the normal pressure of the corresponding axle is as follows:
the process is carried out under the critical condition that the revolution of the planetary gear train is about to occur:
in summary, under the starting or accelerating working condition of the vehicle in the flat ground running state, the front and rear axle motors are cooperatively controlled, the front and rear axle torque distribution coefficient s is taken as a control target, and s is:
the torque of the motor can be fully utilized, and the vehicle can be started and advanced at the maximum acceleration a under the condition that the planet carrier does not revolve. a ismaxComprises the following steps:
therefore, when the vehicle starts or runs with acceleration without obstacles, the torques of the power mechanisms on both sides of the front and rear shafts should be controlled to satisfy:
and controlling the torque distribution coefficient s of the front and rear shafts to satisfy:
(1.3) when the vehicle runs at a constant speed or accelerates on a flat ground, eight Mecanum wheels in four groups are grounded, and the Mecanum wheels can enable the chassis of the vehicle to move omnidirectionally. The mecanum wheels are arranged in an O-shape, and the vehicle can reach the states of forward movement, transverse movement, oblique movement, spinning and the like by controlling the rotating speed of the four groups of wheels, as shown in fig. 6 and 7. The rotating speed of the Mecanum wheel set is controlled to meet the following conditions:
ωi＝ωi1＝ωi2＝ωi3，i＝1，2，3，4；
wherein, ω is1Is the rotational speed, omega, of the left front Mecanum wheel set2For the speed of rotation, omega, of the right front Mecanum wheel set3Is the rotation speed, omega, of the left rear Mecanum wheel set4The rotation speed of the rear right Mecanum wheel group; r is the grounding radius of the Mecanum wheel; y is half of the wheelbase; x is half of the distance between the grounding points of the left and right wheels, omegaiFor the speed of the ith Mecanum wheel set, ωi1For the speed, ω, of the first Mecanum wheel in the ith Mecanum wheel seti2For the speed, ω, of the second Mecanum wheel of the ith Mecanum wheel seti3For the speed of rotation of the third Mecanum wheel of the ith Mecanum wheel set, VXFor longitudinal running speed of vehicle, VYAs the transverse travel speed, ω, of the vehicleoIs the vehicle spin angular velocity.
And then determining the rotating speed of the output shaft of the corresponding motor as the rotating speed of the Mecanum wheel multiplied by the transmission ratio of the chain wheel and the gear.
The above formula is an inverse solution equation of the motion of the background disc under an ideal condition, and the angular velocity of each group of Mecanum wheels of the vehicle under the ideal condition can be obtained only by knowing the translation velocity and the rotation velocity of the motion center of the vehicle to each direction. Therefore, when the vehicle is controlled to travel, the travel speed and the spin angular speed of the vehicle on the X axis (transverse direction) and the Y axis (longitudinal direction) are used as control targets, after the targets are determined, the controller calculates the target rotation speed of each mecanum wheel set and the target rotation speed of the corresponding motor by using the above formula, and outputs a control signal to each motor.
(2.1) when the vehicle runs in an obstacle (in the obstacle crossing process, the vehicle is in a low-speed low-acceleration state, so that the influence of acceleration is not considered), the power mechanism (servo motor) needs to provide enough torque to make the planetary gear train revolve and cross the obstacle, and the torque of the power mechanism on the two sides of the front shaft and the rear shaft needs to be controlled to meet the following requirements:
wherein,is the inclination angle of the vehicle in the horizontal direction, and H is the height of the mass center when the vehicle is horizontally placed; l is the distance between the front axle and the rear axle of the vehicle; b is the distance between the center of mass and the axis of the rear axle in the horizontal direction when the rear axle is horizontally placed; g is the total gravity of the vehicle during operation, MA1、MA2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the front shaft are respectively; mB1、MB2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the rear shaft are respectively; r iscThe radius of gyration of the Mecanum wheel axis around the planet wheel train center when the planet wheel train revolves;
in order to avoid mutual interference of front and rear axle motors, the torque distribution coefficient s of the front and rear axles is controlled to meet the following requirements:
the control method of the chassis structure of the small vehicle applying the complex terrain, which is designed and developed by the invention, can control the running state of each Mecanum wheel set according to the running road surface condition. The torque and the distribution coefficient of the power mechanisms on both sides of the front and rear axles can be controlled according to the running road surface condition and the running state of the vehicle, so that the running stability of the vehicle is improved.
While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.

Claims (10)

1. A small vehicle chassis structure for use with complex terrain, comprising:
a chassis; and
a plurality of Mecanum wheel sets symmetrically and rotatably supported on both sides of the chassis, the Mecanum wheel sets comprising:
a planet carrier;
a sun gear which is arranged at the center of one side of the planet carrier and can rotate along the axial direction of the sun gear;
the planet gears are uniformly arranged in the circumferential direction of the sun gear and are meshed with the sun gear, and the planet gears can revolve around the sun gear in the axial direction and drive the planet carrier to rotate and can also rotate around the self axial direction;
the first chain wheels are arranged on the other side of the planet carrier, correspond to the planet wheels one by one and are coaxially arranged, and the first chain wheels and the corresponding planet wheels synchronously move;
the second chain wheels are respectively arranged on the other side of the planet carrier between the first chain wheels and can rotate around the axial direction of the second chain wheels;
a chain which is connected with the first chain wheel and the second chain wheel in sequence and is in a tensioning state;
the first chain wheel and the second chain wheel are respectively positioned on two sides of the chain;
the Mecanum wheels are arranged on the other side of the planet carrier, correspond to the second chain wheels one by one and are coaxially arranged, and the Mecanum wheels and the corresponding second chain wheels synchronously move;
and the output end of the power mechanism is coaxially and fixedly connected with the sun wheel and is used for driving the sun wheel to rotate.
2. A compact vehicle chassis structure using complex terrain according to claim 1, wherein the carrier comprises:
a first frame plate;
the second frame plate is parallel to the first frame plate and arranged at intervals;
the first frame plate and the second frame plate are consistent in structure and are both triangular plate-shaped structures; and
sun gear and planet wheel set up first frame plate lateral surface, first sprocket, second sprocket and chain setting are in first frame plate with between the second frame plate, mecanum wheel sets up the second frame plate outside.
3. A small-sized vehicle chassis structure for applying a complex terrain according to claim 2, further comprising:
the sun wheel shaft fixedly penetrates through the sun wheel, one end of the sun wheel shaft is rotatably arranged in the center of the outer side face of the first frame plate, and the other end of the sun wheel shaft is fixedly connected with the output end of the power mechanism;
the planet shafts can rotatably penetrate through the first carrier plate and the second carrier plate and correspond to the planet wheels one by one;
the planet wheels are coaxially and fixedly arranged on the planet shaft positioned on the outer side of the first frame plate, and the first chain wheel is coaxially and fixedly arranged on the planet shaft positioned between the first frame plate and the second frame plate;
the chain wheel shafts can rotatably penetrate through the first frame plate and the second frame plate and correspond to the second chain wheels one by one;
the second chain wheel is coaxially and fixedly arranged on the chain wheel shaft between the first frame plate and the second frame plate, and the Mecanum wheel is fixedly arranged on the chain wheel shaft on the outer side of the second frame plate.
4. A small vehicle chassis structure using a complex terrain as set forth in claim 3, wherein the power mechanism further comprises:
the bearing seats are arranged on the outer side of the first frame plate at intervals, and the centers of the bearing seats can rotatably penetrate through the output end of the power mechanism;
wherein the sun gear and the planet gear are arranged between the first frame plate and the bearing seat, and the planet shaft can rotate the bearing seat.
5. A compact vehicle chassis structure for complex terrain applications as claimed in claim 1, 2, 3 or 4 wherein there are 4 of said Mecanum wheel sets and symmetrically rotatable supports are provided on said chassis; each Mecanum wheel set is provided with 3 Mecanum wheels and encloses an equilateral triangle.
6. A method of controlling a chassis structure of a small vehicle utilizing complex terrain, comprising:
when the vehicle runs on the flat ground without obstacles, the planet wheels only rotate around the self axial direction, and the first chain wheel and the second chain wheel drive the Mecanum wheel to rotate to drive the vehicle to run;
when the vehicle runs in an obstacle, the planet wheel axially rotates and also axially revolves around the sun wheel, the planet carrier is driven to drive the Mecanum wheel set to rotate, and the vehicle is driven to move forwards and cross the obstacle;
wherein, when the vehicle is traveling, only 2 and only 2 of the Mecanum wheel sets are simultaneously grounded.
7. The control method of a chassis structure of a small vehicle using a complex terrain as set forth in claim 6, wherein the torque of the power unit controlling both sides of the front and rear axles satisfies:
wherein,is the inclination angle of the vehicle in the horizontal direction, and H is the height of the mass center when the vehicle is horizontally placed; l is the distance between the front axle and the rear axle of the vehicle; b is the distance between the center of mass and the axis of the rear axle in the horizontal direction when the rear axle is horizontally placed; g is the total gravity of the vehicle during operation, MA1、MA2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the front shaft are respectively; mB1、MB2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the rear shaft are respectively; r iscThe radius of gyration of the Mecanum wheel axis around the planet wheel train center when the planet wheel train revolves;
and controlling the torque distribution coefficient s of the front and rear shafts to satisfy:
wherein the maximum climbing capability of the vehicleSatisfies the following conditions:
wherein igIs the planetary gear set transmission ratio; i.e. isThe transmission ratio of the chain wheel set is set; d is the Mecanum wheel diameter.
8. A control method of a chassis structure of a small vehicle using a complex terrain as set forth in claim 6, wherein when the vehicle starts or runs with acceleration without obstacles, the torques of the power units controlling both sides of the front and rear axles are satisfied:
wherein L is the distance between the front axle and the rear axle of the vehicle; g is the total gravity of the vehicle during operation, MA1、MA2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the front shaft are respectively; mB1、MB2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the rear shaft are respectively; r iscThe radius of rotation of a Mecanum wheel axis around the center of the planetary gear train during the revolution of the planetary gear train, d is the diameter of the Mecanum wheel, igIs the planetary gear set transmission ratio; i.e. isIs the transmission ratio of the chain wheel set, and H is the height of the mass center when the vehicle is horizontally placed;
and controlling the torque distribution coefficient s of the front and rear shafts to satisfy:
and controlling the acceleration a of the vehicle to satisfy:
wherein m is0Is the total mass of the vehicle when in operation.
9. The method for controlling a chassis structure of a small vehicle using complex terrains as claimed in claim 7 or 8, wherein when the vehicle is started at a constant speed or is driven at an accelerated speed on a flat ground, the rotation speed of the Mecanum wheel set is controlled to satisfy the following conditions:
ωi＝ωi1＝ωi2＝ωi3，i＝1，2，3，4；
wherein, ω is1Is the rotational speed, omega, of the left front Mecanum wheel set2For the speed of rotation, omega, of the right front Mecanum wheel set3Is the rotation speed, omega, of the left rear Mecanum wheel set4The rotation speed of the rear right Mecanum wheel group; r is the grounding radius of the Mecanum wheel; y is half of the wheelbase; x is half of the distance between the grounding points of the left and right wheels, omegaiFor the speed of the ith Mecanum wheel set, ωi1For the speed, ω, of the first Mecanum wheel in the ith Mecanum wheel seti2For the speed, ω, of the second Mecanum wheel of the ith Mecanum wheel seti3For the speed of rotation of the third Mecanum wheel of the ith Mecanum wheel set, VXFor the transverse running speed of the vehicle, VYAs the longitudinal running speed, ω, of the vehicleoIs the vehicle spin angular velocity.
10. The control method of a chassis structure of a small vehicle using a complex terrain as set forth in claim 6, wherein the torque of the power mechanism controlling both sides of the front and rear axles satisfies:
wherein,is the inclination angle of the vehicle in the horizontal direction, and H is the height of the mass center when the vehicle is horizontally placed; l is the distance between the front axle and the rear axle of the vehicle; b is the distance between the center of mass and the axis of the rear axle in the horizontal direction when the rear axle is horizontally placed; g is the total gravity of the vehicle during operation, MA1、MA2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the front shaft are respectively; mB1、MB2The torque of the power mechanism at the left side and the torque of the power mechanism at the right side of the rear shaft are respectively; r iscThe radius of gyration of the Mecanum wheel axis around the planet wheel train center when the planet wheel train revolves;
and controlling the torque distribution coefficient s of the front and rear shafts to satisfy:
CN201910920431.2A 2019-09-27 2019-09-27 A kind of small vehicle chassis structure and its control method using complicated landform Pending CN110525534A (en)

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