Device and method for detecting dynamic characteristics of omnidirectional ball wheel

Abstract

The invention discloses a device and method for detecting the dynamic characteristics of an omnidirectional ball wheel, comprising three dynamic characteristics detection mechanisms obliquely supported at the lower part of the outer shell of a spherical robot, the outer shell being driven to rotate omnidirectionally by the omnidirectional wheel mechanism, the axes of the three dynamic characteristics detection mechanisms extending upward and intersecting at the center of the outer shell, and the axes of the three dynamic characteristics detection mechanisms being orthogonal to each other, each dynamic characteristics detection mechanism comprising a six-dimensional force sensor coaxially mounted on an axial telescopic component, an inflatable airbag being coaxially mounted on the six-dimensional force sensor, the axial telescopic component being mounted on a support block, the support block being mounted on a support table through a radial sliding pair and being locked in a support position, at the support position, the axial telescopic component bringing the inflated airbag into close contact with the outer shell through the six-dimensional force sensor; each six-dimensional force sensor measures its full force information, establishes its connection with the coordinate system of the center of the outer shell, and introduces a rotation transformation matrix for simplified calculation.

Description

Technical Field

[0001] The invention relates to the detection of characteristics of moving parts, in particular to a device and a method for detecting the dynamic characteristics of an omnidirectional spherical wheel. Background Art

[0002] Four-wheeled vehicles are widely used as transportation tools in people's daily lives. Common car wheels can only rotate around the axis perpendicular to the wheel plane, so they usually cannot move sideways, which easily limits the flexibility of parking and quick avoidance. The omnidirectional wheel spherical robot has the characteristics of small size, lightness and flexibility. It is a rolling robot mechanism that can walk freely in all directions, which can provide ideas for the design of car wheels.

[0003] The utility model patent application numbered 201621419401.1, "Spherical Robot Outer Ball Motion Test Device", discloses a method of measuring the motion parameters of the outer spherical shell through measurement and control components such as incremental photoelectric encoders, thereby detecting the motion parameters (rotation direction, rotation angle and rotation speed) of the outer ball of the spherical robot. The device helps to detect the motion parameters of the spherical robot, and the state of the controlled system is fed back through the detected data to adjust the control parameters and better control the motion of the outer ball.

[0004] However, the utility model patent can only detect the kinematic parameters of the outer ball of the spherical robot, but cannot measure the dynamic parameters such as the force and torque provided by the outer ball of the spherical robot. From the current technical equipment, there is a lack of relevant dynamic characteristic detection, and there is no special testing device to complete the above work, which to a certain extent limits the development of omnidirectional ball wheel research. Summary of the invention

[0005] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to propose a device and method for detecting the dynamic characteristics of an omnidirectional spherical wheel to establish and verify the relationship between the dynamic characteristics of the outer shell of a spherical robot and the driving mechanism.

[0006] A device for detecting the dynamic characteristics of an omnidirectional ball wheel that can solve the above-mentioned technical problems, wherein the technical solution thereof includes three dynamic characteristic detection mechanisms obliquely supported on the lower part of the outer shell of a spherical robot, wherein the outer shell is driven to rotate omnidirectionally through the omnidirectional wheel mechanism, and the axes of the three dynamic characteristic detection mechanisms are extended upward and intersect at the center of the outer shell, and the axes of the three dynamic characteristic detection mechanisms are orthogonal to each other, wherein each dynamic characteristic detection mechanism includes a six-dimensional force sensor coaxially mounted on an axial telescopic component, an inflatable airbag is coaxially mounted on the six-dimensional force sensor, and the axial telescopic component is mounted on a support block, and the support block is mounted on a support platform through a radial sliding pair and locked in a support position, and at the support position, the axial telescopic component uses the six-dimensional force sensor to bring the inflated airbag into close contact with the outer shell.

[0007] One structure of the axial telescopic assembly includes a U-shaped frame and a screw rod arranged in the U-shaped frame, the U-shaped frame is installed on the base plate through an axial sliding pair, the base plate is installed on the support block, the six-dimensional force sensor is installed on the upper end of the U-shaped frame, the upper part of the U-shaped frame is provided with a screw rod seat plate fixed to the base plate, the lower part of the U-shaped frame is provided with a nut seat connected to the frame body, the upper end of the screw rod is installed on the screw rod seat plate, the rod body of the screw rod is screwed on the nut seat, and a stepper motor is provided on the support block outside the lower end of the U-shaped frame, and the rotating shaft of the stepper motor is connected to the lower end of the screw rod through a coupling.

[0008] Furthermore, the outer spherical shell is installed on the bottom of the automobile chassis through a spherical cage, and the omnidirectional wheel mechanism is arranged on the inner spherical shell inside the outer spherical shell.

[0009] The method for detecting the dynamic characteristics of an omnidirectional spherical wheel using the device for detecting the dynamic characteristics of an omnidirectional spherical wheel of the present invention is to establish a connection between the coordinate system of a six-dimensional force sensor and the coordinate system of the center of the outer spherical shell, and to obtain the full force information generated by the outer spherical shell under the drive of the omnidirectional wheel mechanism through a simplified calculation of the spatial force system toward the center of the sphere.

[0010] Beneficial effects of the present invention:

[0011] 1. The device and method for detecting the dynamic characteristics of the omnidirectional spherical wheel of the present invention can conveniently measure the dynamic parameters of the outer shell of the spherical robot by establishing a spatial rectangular coordinate system and simplifying the calculation of mechanical characteristics.

[0012] 2. The present invention solves the problem that it is inconvenient to directly measure the dynamic characteristics of the outer shell of a spherical robot, and can provide detection parameters for the full force information of the outer shell of a spherical robot of different sizes, thereby better debugging the spherical robot and improving the applicable scope and sensitivity of the spherical robot in actual work. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is an axonometric view of an embodiment of the present invention.

[0014] Figure 2 for Figure 1 A schematic diagram of the structure after the outer spherical shell is removed in an embodiment.

[0015] Figure 3 for Figure 1 A schematic structural diagram of a dynamic characteristic detection mechanism in an implementation manner.

[0016] Figure 4 for Figure 1 A schematic diagram of the installation of the support block on the support platform in the implementation manner.

[0017] Figure 5 for Figure 1A schematic diagram of the force acting on the dynamic characteristic detection mechanism and the bull's eye wheel supporting the outer spherical shell in the implementation method.

[0018] Figure 6(a) shows Figure 1 A simplified diagram of a coordinate system established in an implementation manner.

[0019] FIG6( b ) is a view taken along the direction A in FIG6( a ).

[0020] Figure 7 for Figure 1 Coordinate diagram of a six-dimensional force sensor in an implementation manner.

[0021] Figure number identification: 1. Outer spherical shell; 2. Dynamic characteristic detection mechanism; 3. Six-dimensional force sensor; 4. Airbag body; 5. Support block; 6. Support platform; 7. U-shaped frame; 8. Bottom plate; 9. Screw seat plate; 10. Nut seat; 11. Stepper motor; 12. Screw; 13. Spherical cage; 14. Omnidirectional wheel drive mechanism; 15. Automobile chassis; 16. Inner spherical shell; 17. Bull's eye wheel; 18. Electromagnet outside the ball; 19. Electromagnet inside the ball 19; 20. Radial sliding pair; 21. Inner ball rack. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described below in conjunction with the embodiments shown in the accompanying drawings.

[0023] The device for detecting the dynamic characteristics of an omnidirectional spherical wheel of the present invention comprises three dynamic characteristics detection mechanisms 2 obliquely supported at the lower part of an outer spherical shell 1 of a spherical robot, the three dynamic characteristics detection mechanisms 2 are evenly arranged on a support platform 6 around a vertical circumference passing through the center of the outer spherical shell 1, the axes of the three dynamic characteristics detection mechanisms 2 are extended upward and intersect at the center of the outer spherical shell 1 (point O), and the axes of the three dynamic characteristics detection mechanisms 2 are orthogonal to each other to eliminate the influence of torque, the outer spherical shell 1 is installed at the bottom of a car chassis 15 through a spherical cage 13 (half surrounded by the middle and upper part of the outer spherical shell 1), and an inner spherical shell 16 (upper half shell) is arranged in the outer spherical shell 1 at the same center. The bull's eye wheels 17 evenly distributed between the spherical cage 13 and the inner spherical shell 16 limit the outer spherical shell 1, and the bottom of the automobile chassis 15 above the top of the outer spherical shell 1 is provided with an outer spherical electromagnet 18 (in the form of an energized coil) installed on the outer cross axis of the ball (directed downward), and the inner ball rack 21 in the inner spherical shell 16 is centrally provided with an inner spherical electromagnet 19 (directed upward and directly opposite to the outer spherical electromagnet 18) installed on the inner cross axis of the ball. The inner ball rack 21 is also provided with three omnidirectional wheel driving mechanisms 14 (evenly distributed around the circumference) acting on the lower spherical inner shell of the outer spherical shell 1. Under the joint drive of the three omnidirectional wheel driving mechanisms 14, the outer spherical shell 1 can be rotated omnidirectionally, such as Figure 1 , Figure 2 , Figure 5 shown.

[0024] Each dynamic characteristic detection mechanism 2 includes an airbag body 4, a six-dimensional force sensor 3 and an axial telescopic assembly, the axial telescopic assembly includes a U-shaped frame 7, a screw nut transmission pair (including a screw 12 and a nut seat 10) and a stepper motor 11, the U-shaped frame 7 is installed on the base plate 8 through an axial sliding pair, the base plate 8 is fixed to the middle and upper part of the oblique end surface of the support block 5, the stepper motor 11 is fixed to the lower part of the oblique end surface of the support block 5, the support block 5 is installed and locked on the support platform 6 through a radial sliding pair 20, and the nut seat 10 is fixed to the U-shaped frame 7, the screw rod 12 (coaxial with the corresponding dynamic characteristic detection mechanism 2) is screwed into the nut seat 10, the lower end of the screw rod 12 is connected to the rotating shaft of the stepping motor 11 through a coupling, the upper end of the screw rod 12 is installed on the screw rod seat plate 9 on the bottom plate 8, the screw rod seat plate 9 is in the U-shaped frame 7, and the bottom of the U-shaped frame 7 is provided with an axial groove to avoid the connection part between the screw rod seat plate 9 and the bottom plate 8, the lower end of the six-dimensional force sensor 3 is coaxially installed on the upper end of the U-shaped frame 7, and the airbag body 4 is coaxially installed on the upper end of the six-dimensional force sensor 3, as shown in FIG. Figure 1 , Figure 3 , Figure 4 , Figure 5 shown.

[0025] According to the diameter of the outer spherical shell 1, the radial positions of the three support blocks 5 are adjusted and locked, and the three stepping motors 11 are started synchronously to drive the three screw rods 12 to rotate. The three nut seats 10 move along the corresponding screw rods 12 to drive the corresponding U-shaped frames 7 to move obliquely upward to adjust the three airbags 4 to the appropriate positions synchronously, and the airbags 4 are inflated synchronously to make them closely contact with the outer shell surface of the lower part of the outer spherical shell 1. The tightness of the close contact of the three airbags 4 is such that the outer spherical shell 1 is just in a critical state of not rotating, such as Figure 1 , Figure 5 shown.

[0026] The six-dimensional force sensor 3 can simultaneously detect the full force information in three-dimensional space (Cartesian coordinate system), that is, three force components and three torque components, such as Figure 7 As shown, we can get a vector L = (F x ,F y ,F z ,M x ,M y ,M z ) T .

[0027] The full force information measured by the six-dimensional force sensor 3 is simplified to the ball center O. The specific solution is:

[0028] Step 1: Establish the coordinate system

[0029] Since the coordinate systems of the three six-dimensional force sensors 3 are in different directions, the vectors of the measured full force information need to be calculated in the same coordinate system when simplified. Therefore, it is necessary to establish a coordinate system and then perform the corresponding rotation transformation. FIG6(a) shows the corresponding coordinate system, where O1, O2, and O3 are the points of action of the three six-dimensional force sensors 3, and their Z axes always point to the center point O (as shown in FIG6(a)). Figure 5 As shown in Figure 6(b), a plane passing through the center of the sphere O and parallel to the ground is shown. To facilitate the description of the directions of the three axes of the coordinate system, the directions of the coordinate axes on the plane, where OO1, OO2, and OO3 directions (dashed lines) are the projections of the xz plane on the plane after the origin of the three six-dimensional force sensor 3 coordinate systems is translated to the center of the sphere. For the convenience of description, the vector radius from point O1, O2, and O3 to point O is r1, r2, and r3, respectively, and the angle between the Z axis of the O1, O2, and O3 coordinate systems and the Z axis of the O system is θ.

[0030] Step 2: Introduce the coordinate rotation transformation matrix:

[0031] The rotation from O1 to O is to first rotate around the y-axis by an angle of θ, then rotate 60° around the Z-axis based on the new coordinate system, and finally move the origin of the coordinate system to the center of the sphere. The rotation transformation from O to O1 is the inverse transformation of the above process, that is:

[0032] The rotation from O2 to O is to first rotate around the y-axis by an angle of θ, then rotate around the Z-axis by -60° on the basis of the new coordinate system, and finally move the origin of the coordinate system to the center of the sphere. The rotation transformation from O2 to O is the inverse transformation of the above process, that is:

[0033] The rotation transformation from O3 to O is to first rotate around the y-axis by an angle of θ, then rotate 180° around the Z-axis based on the new coordinate system, and finally move the origin of the coordinate system to the center of the sphere. The rotation transformation from O to O3 is the inverse transformation of the above process, that is:

[0034] Step 3: Simplify the calculation

[0035] According to the principle of simplifying any force system in space to a point, each force is translated to the simplified center in turn, and a corresponding couple is added at the same time. Figure 5 It can be seen that the supporting effect of each supporting structure (bull's eye wheel, detection mechanism) is that the force axis of the outer spherical shell passes through the center of the sphere, so the influence of the torque generated by the outer spherical shell center can be eliminated.

[0036] The simplified force vector from point O1 to point O is: where F′1=F x1 +F y1 +F z1 , the total torque after simplification is where τ′1=M x1 +M y1 +M z1 +F x1 ×r1+F y1 ×r1. Similarly, after point O2 is simplified to point O where F′2=F x2 +F y2 +F z2 , torque where τ′2=M x2 +M y2 +M z2 +F x2 ×r2+F y2 ×r2; after point O3 is simplified to point O where F′3=F x3 +F y3 +F z3 , torque where τ′3=M x3 +M y3 +M z3 +F x3 ×r3+F y3 ×r3. Then the principal vector and principal moment of the sphere center O are F = ∑F i ,τ=∑τ i (i=1,2,3).

[0037] At this point, the full force information generated by the outer spherical shell 1 driven by the omnidirectional wheel driving mechanism 14 can be obtained.

Claims

1. A device for detecting the dynamic characteristics of an omnidirectional spherical wheel, comprising three dynamic characteristics detection mechanisms (2) obliquely supported at the lower part of an outer spherical shell (1) of a spherical robot, wherein the outer spherical shell (1) is driven to rotate omnidirectionally by an omnidirectional wheel mechanism (14), and the axes of the three dynamic characteristics detection mechanisms (2) are extended upward and intersect at the center of the outer spherical shell (1), and the axes of the three dynamic characteristics detection mechanisms (2) are orthogonal to each other, and characterized in that: Each dynamic characteristic detection mechanism (2) comprises a six-dimensional force sensor (3) coaxially mounted on an axial telescopic component, an inflatable airbag (4) coaxially mounted on the six-dimensional force sensor (3), the axial telescopic component is mounted on a support block (5), the support block (5) is mounted on a support platform (6) through a radial sliding pair and locked in a supporting position, and in the supporting position, the axial telescopic component brings the inflated airbag (4) into close contact with the outer spherical shell (1) through the six-dimensional force sensor (3).

2. The device for detecting the dynamic characteristics of an omnidirectional spherical wheel according to claim 1, characterized in that: The axial telescopic assembly comprises a U-shaped frame (7) and a screw rod (12) arranged in the U-shaped frame (7); the U-shaped frame (7) is mounted on a base plate (8) through an axial sliding pair; the base plate (8) is mounted on a support block (5); the six-dimensional force sensor (3) is mounted on the upper end of the U-shaped frame (7); the upper part of the U-shaped frame (7) is provided with a screw rod seat plate (9) fixed to the base plate (8); the lower part of the U-shaped frame (7) is provided with a nut seat (10) connected to the frame body; the upper end of the screw rod (12) is mounted on the screw rod seat plate (9); the rod body of the screw rod (12) is screwed into the nut seat (10); a stepping motor (11) is arranged on the support block (5) outside the lower end of the U-shaped frame (7); the rotating shaft of the stepping motor (11) is connected to the lower end of the screw rod (12) through a coupling.

3. The device for detecting the dynamic characteristics of an omnidirectional spherical wheel according to claim 1 or 2, characterized in that: The outer spherical shell (1) is installed on the bottom of the automobile chassis (15) through a spherical cage (13), and the omnidirectional wheel mechanism (14) is arranged on the inner spherical shell (16) inside the outer spherical shell (1).

4. A method for detecting the dynamic characteristics of an omnidirectional ball wheel, characterized in that A device for detecting the dynamic characteristics of an omnidirectional spherical wheel as described in claim 1 or 2 is used, by establishing a connection between the coordinate system of a six-dimensional force sensor (3) and the coordinate system of the center of the outer spherical shell (1), and by simplified calculation of the spatial force system toward the center of the sphere, the full force information generated by the outer spherical shell (1) when driven by the omnidirectional wheel mechanism (14) is obtained.

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