Mobile robot with adjustable traction weight

Abstract

The present invention relates to a basic mobile robot (1) in which the weight on the drive wheels (6) can be adjusted to achieve the best traction and braking performance of the mobile robot (1) for the relevant application. By means of the inventive design of the bogie arm (4) and the modular traction counterweight (9), the weight force acting on the drive wheel (6) and the resulting friction force can be increased by attaching one or more traction weight modules (13) to the bogie arm extension (12), while the weight force generated on the (front) castor (7) is reduced due to the cantilever effect. Therefore, it is relatively easy to obtain sufficient traction on the drive wheel (6) for the intended application without affecting safety and with minimal impact on the overall energy efficiency of the mobile robot (1). The mobile robot (1) can be configured for different applications, including transporting goods loaded on top of the mobile robot (1), cart pulling or autonomously hauling materials indoors.

Description

Technical Field

[0001] The present invention relates to a basic mobile robot that can be configured for different applications, including the transportation of cargo loaded on top of the mobile robot, cart pulling, or autonomous hauling of materials indoors. More specifically, the present invention relates to a mobile robot in which the weight on the drive wheels can be adjusted to achieve optimal traction and braking performance of the mobile robot for the relevant application. Background Art

[0002] The transportation of items within a structure or between multiple structures has become problematic to some extent. Today, many transportation options exist as commercial products, such as conveyor belts, pneumatic tubes, universal carts, and mobile robots. A mobile robot or automated guided vehicle (AGV) is a vehicle equipped with a drive system under computer control that allows autonomous guidance between two locations.

[0003] Towing trailers with towing devices mounted on AGVs are well known in the art. Typically, a commercial hook and ball are mounted on one end of the AGV, typically the rear, where a trailer including a releasable socket and towing bar is connected.

[0004] Robots and automated vehicles for delivering or transporting materials indoors have been developed and utilized in several applications. A well-known application is automated mail delivery vehicles and robots.

[0005] Patent application US2004093650A1 (and corresponding patent US7066291B2) discloses a mobile robot system for performing multiple individual operations, including at least one autonomous wheeled mobile robot having at least one wheel drive motor, an onboard computer; means for navigation, orientation and maneuvering in an environment with moving obstacles; a sensor system; and a wireless communication system for receiving and sending signals. The mobile robot system disclosed in US2004093650 / US7066291B2 can be used to haul materials on various carts or trucks using a coupling hook hook rod as a cart attachment mechanism. At the same time, the cart attachment mechanism US2004093650 cannot move freely on the pivot point and is not suitable for hauling a cart on an uneven support; for example, on a door frame.

[0006] A mobile robot usually has one or more drive wheels and one or more support wheels, such as casters.

[0007] A popular configuration is to place the drive wheels in the middle of each of the two long sides of a preferably rectangular mobile robot chassis. Each drive wheel is driven by a separate controllable motor. In addition, the robot is supported by four casters; one at each corner of the chassis.

[0008] The mobile robot can be driven bidirectionally and steered by driving the drive wheels at different speeds or in opposite directions relative to each other. Patent application WO2016165721 discloses a robotic cart-pulling vehicle for automatically docking and pulling a cart, such as a wheeled hospital cart, for example, for linens. Specifically, the robotic vehicle is equipped with a gripping device for holding the cart. The vehicle has a rectangular chassis with a drive wheel placed in the middle of each of the two long sides of the chassis, four castors; one at each corner of the chassis.

[0009] At the same time, the pulling force of the vehicle according to WO2016165721 is limited by the available friction between the drive wheels and the bracket. If a certain application requires better traction, the friction between the drive wheels and the bracket can be increased by adding additional weight on top of the robot. However, this additional weight has a negative impact on the overall energy efficiency and safety of the robot.

[0010] In a preferred version, each of the two drive wheels is mechanically interconnected with a (front) castor wheel via a bogie arm. The robot chassis is supported by the pivot point of the bogie arm and a set of rear castors. Each drive wheel is driven by a separate controllable motor.

[0011] The bogie construction allows the robot to move on uneven surfaces.

[0012] The CN208774905U registered utility model (and corresponding application CN108725626) shows an example of this basic configuration. It shows an AGV whose drive wheels are placed in the middle of the two long sides of a rectangular mobile robot chassis. Each drive wheel is driven by a motor. In addition, the mobile robot is supported by four castors; one at each corner of the chassis. Each of the two drive wheels is mechanically interconnected to the (front) castor via a bogie arm. The robot chassis is supported by the pivot point of the bogie arm and a set of rear castors.

[0013] To drive (and stop) a mobile robot, including its possible top load and / or possible cart, without slipping, there must be a certain amount of friction between the drive wheels and the surface. The friction generated between the drive wheels and the ground is determined by the coefficient of friction between the drive wheel surface and the floor surface and the weight force acting on the drive wheels.

[0014] Drive wheel slippage can lead to inefficient transport and poor braking performance.

[0015] Furthermore, the navigation system of the mobile robot is usually based on or at least supports an odometer that receives input from the drive motor, drive gear, drive shaft and / or drive wheels. Therefore, any slip of the drive wheels will lead to erroneous information about the traveled distance.

[0016] CN208774905U proposes to arrange a set of adjustable preload springs between the chassis frame and the bogie arm. By adjusting the load of these springs, the distribution of gravity acting on the drive wheel and the front castor wheel can be changed. The friction between the drive wheel and the support can be increased. However, the friction between the front castor wheel and the support is reduced, and the contact is finally reduced, which will have a negative impact on the driving / steering ability of the vehicle.

[0017] If the mobile robot itself (including possible top loads) does not have sufficient weight to provide the required friction for the drive wheels in a given application, it is known to add additional weight on top of the mobile robot. However, any additional weight generally reduces the overall efficiency of the mobile robot and results in shorter operating time between battery charges of the robot.

[0018] Extra weight on top of the robot may also compromise the overall safety of the mobile robot. Adding extra weight may result in a higher center of mass point, which in turn may lead to a higher risk of the mobile robot tipping over during braking.

[0019] On a mobile robot with 2 drive wheels and 4 casters, any additional weight will act on the drive wheels, but also on at least one, and usually two, of the supporting casters.

[0020] The added weight on the castors does again increase the need for better traction on the drive wheels. Therefore, a relatively large amount of weight needs to be added to get enough traction on the drive wheels. The extra weight increases the energy consumption of moving the robot and can challenge braking performance and potentially increase the risk of tipping.

[0021] The object of the present invention is to improve upon the prior art and to provide a basic mobile robot whose traction on the drive wheels can be relatively easily optimized for the intended application without compromising safety and with minimal impact on overall operational efficiency. Summary of the invention

[0022] The present invention provides an improved mobile robot for automated docking and pulling / hauling carts and similar trucks from one location to another, or for transporting a payload on top of the mobile robot. The mobile robot implements a navigation system for navigating in corridors. The navigation system preferably includes an odometer that receives input from the drive motors. The mobile robot also includes one or more sensors for indicating the position of the robot relative to the surrounding environment to avoid unnecessary impacts.

[0023] By means of the inventive design of the bogie arm connecting the drive wheel and the (front) castor wheel and the modular traction counterweight, the weight force acting on the drive wheel and the friction force generated can be increased by attaching one or more counterweight modules to the extension of the bogie arm, while the weight force generated on the (front) castor wheel is reduced due to the cantilever effect. Therefore, it is relatively easy to achieve sufficient traction on the drive wheel for the intended application without compromising safety and with minimal impact on the overall energy efficiency of the mobile robot.

[0024] By placing the center of mass of the traction weight at a level lower than the center of gravity of the entire mobile robot, the risk of tipping over during braking or turning situations is reduced.

[0025] By positioning the center of mass of the traction weight below the pivot point of the bogie arm and as low as possible, the inertia of the traction weight helps press the drive wheel down during braking, increasing friction and braking performance at the drive wheel.

[0026] As a result, the present invention can easily optimize the traction, navigation, braking performance and safety of a mobile robot for a given application, while having minimal impact on the overall energy efficiency of the robot. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to better understand the present invention and appreciate its practical application, the following drawings are provided and referenced. The drawings are given as examples only and should in no way limit the scope of the present invention.

[0028] Figure 1a depicts a mobile robot and right bogie arm having a pivot point, rear caster, traction weight module, drive wheel, front caster, and traction weight mounted on a bogie arm extension;

[0029] Figure 1b presenting an oblique bottom / right side view of the right drive wheel and right front caster wheel;

[0030] Figure 2a The available traction of the driving wheels of a mobile robot is presented, which is proportional to the normal force exerted by the robot's weight on the ground and depends on the coefficient of friction between the ground and the wheel threads;

[0031] Figure 2b Presents the maximum torque that can be transmitted to the ground through the drive wheels;

[0032] Figure 2c The normal force of the driving wheel on the ground comes from the weight of the robot pressing on the pivot point of the bogie and the weight of the bogie itself;

[0033] Figure 2d The force at the pivot point comes from the load on the robot and the robot mass;

[0034] Figure 2e It is presented that the addition of a set of traction weights on a set of bogie arm extensions behind the drive wheels increases the weight force acting on the drive wheels and reduces the weight force acting on the front casters;

[0035] Figure 3a -c presents different side views (a, b, c) of the right bogie arm with the pivot point, rear castor, traction weight, drive wheel, front castor, mounted on the bogie arm extension:

[0036] (a) Bogie arm viewed from the outside,

[0037] (b) Bogie arm viewed from the inside,

[0038] (c) The bogie arm is viewed from the right side and below the robot, showing the housing covering the bogie arm from the right side;

[0039] Figure 4 Exploded view showing the right side drive motor (including the gearbox for the drive motor), the complete truck arm (with its pivot point and truck arm extension adapted for attachment of the traction counterweight), the front castor, the drive wheel, the drive wheel bearing, the means for attaching the drive wheel (rings and screws), and a traction counterweight consisting of 5 counterweight modules with a set of aligned bolt holes that can be aligned with a set of matching holes on the truck arm extension for bolting the counterweight modules to the truck arm extension. One end of the traction counterweight and the counterweight module are shaped to fit the gearbox for the drive motor, respectively.

[0040] Figures – Reference numerals

[0041] 1. Mobile robot;

[0042] 2 Optimal front end for mobile robots;

[0043] 3. Optimal backend for mobile robots;

[0044] 4 Bogie arms;

[0045] 5 Pivot point of the steering gear arm;

[0046] 6 driving wheels;

[0047] 7 front castors;

[0048] 8 rear casters;

[0049] 9 Traction counterweight (including counterweight module);

[0050] 10 Motor / brake, which is connected to the drive wheel through a gearbox;

[0051] 11 Attachment holes for mounting towing weights;

[0052] 12 bogie arm extension;

[0053] 13. Counterweight module for traction counterweight;

[0054] 14 Robot chassis;

[0055] 15 robot top;

[0056] 16. Housing (covering at least the sides of the mobile robot).

[0057] 17 Top module or load on top of the robot. DETAILED DESCRIPTION

[0058] This chapter describes the inventive design of the bogie arm 4 and the traction counterweight 9 ( Figure 1a , b), by attaching one or more counterweight modules 13 to the bogie arm extension 12, the weight force acting on the drive wheel 6 and the resulting friction force can be increased, while the weight force acting on the (front) castor 7 is reduced due to the cantilever effect. Therefore, it is relatively easy to achieve sufficient traction on the drive wheel 6 for the intended application without compromising safety and with minimal impact on the overall energy efficiency of the mobile robot 1.

[0059] The available traction of the driving wheel 6 of the mobile robot is proportional to the normal force exerted by the robot's gravity on the ground and depends on the friction coefficient between the ground and the wheel thread ( Figure 2a ):

[0060] F T =F N *μ

[0061] Where μ is the friction coefficient; F N is the normal force.

[0062] The robot drive wheels can transmit torque accordingly. Figure 2b )The maximum torque transmitted to the ground can be described as:

[0063] M 最大 =F T *r

[0064] Where r is the radius of the drive wheel.

[0065] The torque is generated by the motor or brake connected to the drive wheels through the gearbox. If the torque is higher than M 最大 Will slip on the ground.

[0066] Normal force F of the driving wheel on the ground N The weight of the robot pressing on the bogie pivot point and the gravity of the bogie itself ( Figure 2c ):

[0067]

[0068]

[0069] in:

[0070] L 1 ,L 2 ,L 3 ,L 4 is the distance to the reaction force;

[0071] F P is the force due to the weight of the robot without the bogie at the bogie pivot point. Assuming the load is evenly distributed between the left and right bogies, this is the force in the calculation of F P The reason for dividing by 2;

[0072] F g-b is the bogie weight;

[0073] F N-FC is the normal force of the front caster on the ground.

[0074] The forces in the pivot point come from the load on the robot and the robot mass ( Figure 2d ):

[0075]

[0076]

[0077] in:

[0078] F g-l is the force from the weight of the load;

[0079] F g-r is the force from the gravity of the bogieless robot;

[0080] F N-RC is the normal to the ground from the rear caster.

[0081] When a set of counterweight modules 13 is added to a set of bogie arm extensions 12 behind the drive wheels 6, the gravity acting on the drive wheels 6 increases, while the gravity acting on the front casters 7 decreases ( Figure 2e ). Thus, sufficient traction can be achieved with no or at least minimal impact on the performance and without compromising the safety of the robot.

[0082] F g-b =F g-bt +F g-t

[0083]

[0084] in:

[0085] F g-t is the force from the gravity of the traction counterweight 9;

[0086] F g-bt is the force from the weight of the bogie without the traction counterweight.

[0087] By mounting the traction weight 9 directly on the bogie arm extension 12 , the overall mass of the mobile robot 1 can be significantly reduced and still obtain the correct traction as if a larger load 17 were placed on the top surface 15 of the mobile robot 1 .

[0088] When reducing the overall mass of the mobile robot 1 , the efficiency improves and therefore the battery runtime increases, since the powertrain is one of the main consumers of the battery.

[0089] Specifically, a preferred embodiment of the present invention provides:

[0090] ■ A mobile robot 1 having a chassis 14 with a preferred front end 2 and a preferred rear end 3, the mobile robot comprising:

[0091] ○ A pair of driving wheels 6 at the center of the mobile robot 1,

[0092] ■ wherein the drive wheel set 6 is preferably connected to a set of drive motors 10 via a drive shaft and a gearbox,

[0093] Each drive motor 10 can be controlled individually in two directions by the control system of the mobile robot, allowing the robot 1 to be driven in two directions and to rotate (approximately) 360 degrees around its vertical center axis;

[0094] ■ a pair of (front) casters 7, located at a corner of one end (preferably the front end) of the mobile robot 1;

[0095] ■ A set of (rear) castors 8 at the other (preferably rear) end of the mobile robot 1:

[0096] o wherein a pair of drive wheels 6 are mechanically interconnected to a pair of (front) castors 7 via a pair of bogie arms 4 having a pivot point 5,

[0097] ○ The robot chassis 14 is supported by the bogie arm 4 at the pivot point 5 and the two (rear) castors 8,

[0098] ■ wherein the bogie arm 4 has a bogie arm extension 12 which projects behind the axis of the drive wheel 6 (seen from the preferably front end 2 of the mobile robot),

[0099] ■ wherein the bogie arm extension 12 is suitable for mounting a traction counterweight 9, the traction counterweight 9 comprising one or more counterweight modules 13;

[0100] ■ a top surface 15 suitable for mounting various top modules or payloads 17 to the chassis of the robot 14;

[0101] ■Optional types of top module 17 may include:

[0102] Attachment mechanism for coupling a cart or wheeled inventory, stand to the mobile robot,

[0103] ·Transport platforms, boxes or racks,

[0104] Manipulators, such as robotic arms,

[0105] Lifting mechanism for lifting pallets or inventory racks

[0106] and / or conveyor mechanisms for loading / unloading items;

[0107] ■ a housing 16 covering at least the sides of the mobile robot 1 , wherein at least parts of the housing 16 at the sides of the robot are removable in order to provide easy access to the one or more traction weights 9 .

[0108] In alternative embodiments, the exact form of the bogie arm extension 12 may be adapted to the size and shape of the mobile robot 1 and its intended application. The length and form of the portion of the bogie arm extension 12 carrying the traction counterweight 9 may vary to allow attachment of different numbers, types and sizes of counterweight modules 13.

[0109] The traction counterweight 9 is preferably designed as one or more counterweight modules 13 , preferably metal plates, suitable for being fixed to the bogie arm extension 12 .

[0110] The bogie arm extension 12 and the counterweight modules 13 are preferably provided with one or more aligned holes 11 for fixing an optimum number of counterweight modules 13 to the bogie arm extension 12 ( Figure 4 ).

[0111] In a preferred embodiment, one end of one or more traction weights 9 has a shape that matches the shape of the drive motor 10 and / or a possible gearbox, so that the available space for placing additional weight modules 13 can be utilized.

[0112] Furthermore, the bogie arm extension 12 may be adapted to allow the traction weight 9 to be attached to the bogie arm 4 at different distances from the center of the drive wheel 6. Thus, by adding minimal additional weight to the mobile robot 1, the traction of the drive wheel 6 is optimized for a given application of the mobile robot 1.

[0113] With this solution it is achieved that the increase in weight does increase the traction on the drive wheels without increasing the friction on the supporting castors. Furthermore, an improved breaking performance is achieved while reducing the risk of tilting.

[0114] Reference List

[0115] Patent Literature

[0116] Patent application US2004093650A1 / Patent US7066291B2. G.Martins et al. Robot system (G.Martins et al. Robot system).

[0117] Patent application WO2016165721. Niels Jul Jacobsen. Robotic cart pulling vehicle for automated pulling of carts

[0118] · Registered utility model CN208774905U / application CN108725626. Zeng Chao. A kind of chassis structure of AGV.

Claims

1. A mobile robot (1) having a chassis (14), the chassis (14) having a front end (2) and a rear end (3), comprising at least: ▪ a pair of drive wheels (6), wherein each of the pair of drive wheels (6) is coupled to a respective drive motor of a set of drive motors (10), ▪ a pair of front casters (7) at the front end (2) of the mobile robot, ▪ a pair of rear casters (8) at the rear end (3) of the mobile robot (1), in o each of the pair of drive wheels (6) is mechanically interconnected with a corresponding front castor wheel of the pair of front castors (7) via a bogie arm (4) having a pivot point (5), ○ The chassis (14) of the mobile robot is supported by the bogie arm (4) at the pivot point (5) and the pair of rear castors (8), Features ▪ the bogie arms (4) each comprise a bogie arm extension (12) protruding behind the axis of the drive wheel (6), wherein each bogie arm extension is suitable for mounting one or more traction weights (9), ▪ and one or more traction weights (9), The length and shape of the portion of the bogie arm extension carrying the one or more traction weights (9) can be varied to allow attachment of different numbers, types and sizes of the one or more traction weights.

2. The mobile robot (1) according to claim 1, It is characterized in that The one or more traction counterweights (9) include a counterweight module (13) for configurable weight distribution of the bogie arm extension (12).

3. The mobile robot (1) according to claim 1, It is characterized in that The bogie arm extension (12) can be adapted to allow the traction weight (9) to be attached to the bogie arm (4) at different distances from the centre of the drive wheel (6).

4. The mobile robot (1) according to claim 1, It is characterized in that The center of mass of the traction counterweight (9) is at a level lower than the center of mass of the entire mobile robot (1).

5. The mobile robot (1) according to claim 1, It is characterized in that The center of mass of the traction counterweight (9) is at a level below the pivot point (5) of the bogie arm (4).

6. The mobile robot (1) according to claim 1, It is characterized in that Each drive motor (10) can be controlled individually in two directions by a control system of the mobile robot.

7. The mobile robot (1) according to claim 1, It is characterized in that The mobile robot further comprises a top surface (15) of the chassis (14), the top surface being suitable for mounting a top module (17) on the robot body.

8. The mobile robot (1) according to claim 1, It is characterized in that The mobile robot further comprises a shell (16) covering at least a side surface of the mobile robot (1); wherein at least a portion of the shell (16) at the side surface of the mobile robot (1) is detachable.

9. The mobile robot (1) according to claim 7, It is characterized in that The mobile robot further comprises a top module, wherein the top module (17) comprises at least one of the following: ▪ an attachment mechanism for coupling a cart or wheeled inventory holder to the mobile robot (1), ▪ Shipping platforms, boxes or racks, or ▪ Manipulator, or ▪ A lifting mechanism to raise or lower a pallet or inventory rack, or ▪ Conveyor mechanism for loading / unloading of items.

10. The mobile robot (1) according to claim 9, It is characterized in that The manipulator is a robotic arm.

11. The mobile robot (1) according to any one of claims 1 to 10, in, The pair of drive wheels are coupled to the set of drive motors through a drive shaft and a gearbox.

12. The mobile robot (1) according to claim 2, It is characterized in that The shapes of the traction counterweight block (9) and the counterweight module (13) are respectively adapted to the shape of the drive motor (10) or the shape of the gear box.

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