Underwater robot based on patch type piezoelectric transducer and working method thereof

Abstract

The invention discloses a novel underwater robot based on a patch type piezoelectric transducer, and relates to the field of piezoelectric driving. The device comprises a patch type piezoelectric transducer, a clamping structure, a base body, two tension springs, four bearings, a first axle, a second axle, four wheels and two bearing boxes. The patch type piezoelectric transducer is fixed between two vertical plates of the base body through a clamping structure, two wheel shafts of the wheel are clamped in wheel shaft holes of the base body through bearings and limiting gaskets, and two tension springs are hung on bolts on the two sides of the base body and are in a stretching state, so that two plane driving feet at the bottom of the piezoelectric transducer abut against the two wheel shafts. When the robot works, the patch type piezoelectric transducers are excited, the two plane driving feet at the bottoms of the patch type piezoelectric transducers generate elliptical motion in the same direction, the two wheel shafts are driven to rotate through friction, then the wheels are driven to rotate, and movement of the robot is achieved. According to the technical scheme, the problems that an existing underwater robot is large in size, complex in structure and difficult in dynamic sealing in the high-water-pressure environment are solved.

Description

Technical Field

[0001] This invention relates to the fields of piezoelectric actuation and underwater robots, and more particularly to a novel patch-type piezoelectric actuation underwater robot. Background Technology

[0002] Underwater robots are indispensable tools for seabed exploration, and are mostly wheeled or propeller-driven. They are characterized by their small size, fast response, and simple sealing, playing a vital role in underwater monitoring and deep-sea resource exploration.

[0003] The deep-sea environment presents the challenge of high water pressure; for every 1000 meters increase in depth, the pressure increases by 1 MPa. This high-pressure environment hinders the development of deep-sea exploration. If traditional electromagnetic motors are used for propulsion, the drive components must be sealed with a heavy, pressure-resistant shell to prevent damage and failure under high pressure. Furthermore, the complex transmission structure restricts the miniaturization and high-pressure resistance of underwater robots.

[0004] Piezoelectric actuators generate micron-level elliptical motion on the surface particles of the stator actuator head, and transmit motion between the stator and actuator through friction. Because piezoelectric actuators can operate in aquatic environments after the stator structure is sealed, and can withstand high water pressure of 110MPa; direct drive eliminates the need for a transmission mechanism, which is beneficial for high pressure resistance, lightweight design, and miniaturization. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies mentioned in the background art by providing a novel underwater robot based on a patch piezoelectric transducer.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution;

[0007] A novel underwater robot based on a patch piezoelectric transducer includes a patch piezoelectric transducer, a clamping structure, a base, two tension springs, four bearings, a first axle, a second axle, four wheels, and two load-bearing boxes.

[0008] The patch piezoelectric transducer includes a metal substrate, a connecting beam, and a clamping beam;

[0009] The metal substrate includes a first vibrating beam, a second vibrating beam, a first driving foot, and a second driving foot;

[0010] The first vibration beam and the second vibration beam are two identical cuboids placed symmetrically from left to right. Each cuboid includes four sides (front, back, left, right) and two end faces (top and bottom). The first driving foot and the second driving foot each include a driving end and a connecting end. The driving end is planar and the connecting end is planar. The connecting ends of the first driving foot and the second driving foot are fixedly connected to the lower end faces of the first vibration beam and the second vibration beam, respectively.

[0011] The connecting beam is a symmetrical convex beam, which is set between the first vibrating beam and the second vibrating beam. The left and right end faces of the connecting beam are respectively fixed to the right end face of the first vibrating beam and the left end face of the second vibrating beam.

[0012] The clamping beam is a plate-shaped structure that is symmetrical about the two sides of the structure center and protrudes in the middle. It is set between the first vibration beam and the second vibration beam. The left and right end faces of the clamping beam are fixed to the right end face of the first vibration beam and the left end face of the second vibration beam, respectively. Through holes are opened on the front and rear end faces of the protruding middle for clamping the patch piezoelectric transducer between the clamping structures.

[0013] The first and second vibration beams have piezoelectric ceramic sheets attached to their front and rear sides at the maximum amplitude of the Nth order bending vibration mode in the metal substrate, where N is an even number and is the bending vibration order of the pre-set working mode.

[0014] The piezoelectric ceramic sheet used to generate bending vibration is polarized along its thickness direction; the piezoelectric ceramic sheet that generates bending vibration is polarized from the outer side to the inner side.

[0015] The bottom of the clamping structure is a cuboid boss. Two upright plates for clamping the piezoelectric transducer clamping beam are erected on the front and rear sides of the cuboid boss. The two upright plates have through holes that are aligned with the through holes on the front and rear end faces of the piezoelectric transducer clamping beam. The left and right sides of the cuboid boss at the bottom of the clamping structure are locked between the first and second driving feet of the piezoelectric transducer.

[0016] The base has a rectangular groove at the bottom. The front and rear side plates of the groove have concentric through holes for placing bearings and several bolt holes for placing bolts to facilitate suspension of the tension spring. Several through holes are opened at the bottom for limiting the propulsion device. There is a vertical plate at the center of the front and rear side plates of the base. The two vertical plates have waist-shaped holes for limiting the clamping structure.

[0017] The two tension springs are placed symmetrically on the outside of the two vertical plates of the base. One end of the tension spring is suspended on the bolt that passes through the waist hole on the two vertical plates of the base, and the other end is suspended on the bolt that is fixed to the bolt hole on the front and rear side plates of the bottom groove of the base.

[0018] The four bearings are respectively installed in the bearing holes on the side plate of the cuboid groove at the bottom of the base. The front and rear bearings are placed concentrically, and the inner holes of the left and right bearings are respectively used to place the first wheel axle and the second wheel axle.

[0019] The first and second axles are respectively installed through the left and right bearing holes. The outer edge of the axle is tangent to the driving foot plane at the bottom of the patch piezoelectric transducer. At the same time, the axle has pin holes on the outer side of the front and rear bearing holes to place pins and limit the bearings. The two ends of the axle are stepped to connect to the inner hub of the wheel. Bolt holes are opened on both ends of the axle to install bolts to limit the wheel along the axle axis.

[0020] The four wheels have identical structures. Each wheel includes an inner hub, an outer hub, a shaft, and several blades. The inner and outer hubs are concentrically arranged, with the inner hub having a waist-shaped hole and the outer hub having an annular shape. The blades are evenly installed between the inner and outer hubs, with one end of each blade fixed to the inner hub and the other end fixed to the outer hub. If combined with a buoyancy device to suspend the robot in water, the rotation of the blades will enable the robot to swim in the water. The axle is connected to the inner hub, and the wheel is fixed relative to the axle.

[0021] The two load-bearing boxes have identical structures. Each load-bearing box consists of a rectangular base plate and four side plates that are vertically connected to the base plate. The four side plates and the base plate together form an open-top accommodating space, with one side plate extending out a connecting plate for connection to the base.

[0022] As a further optimization of the patch-type piezoelectric driven underwater mobile robot of the present invention, the four wheels, axles and inner hubs are rotatably connected by an interference fit.

[0023] As a further optimization of the patch-type piezoelectric driven underwater mobile robot of the present invention, the wheel axle and the base body are fitted together by bearings.

[0024] As a further optimization of the patch-type piezoelectric driven underwater mobile robot of the present invention, the four wheels are completely identical in shape and size.

[0025] As a further optimization of the patch-type piezoelectric driven underwater mobile robot of the present invention, the first driving foot and the second driving foot have the same shape and size.

[0026] As a further optimization of the patch-type piezoelectric driven underwater mobile robot of the present invention, the two load-bearing boxes are completely identical in shape and size.

[0027] As a further optimization of the patch-type piezoelectric driven underwater mobile robot of the present invention, the two vertical plates of the base are symmetrically arranged with equally spaced threaded holes for mating with bolts.

[0028] As a further optimization of the patch-type piezoelectric driven underwater mobile robot of the present invention, one end of the tension spring is suspended on the bolt passing through the center hole of the flange, and the other end is suspended on the bolts of the two vertical plates of the base.

[0029] As a further optimization of the patch-type piezoelectric driven underwater mobile robot of the present invention, the bearing is made of zirconia ceramic material.

[0030] The present invention also discloses a method for operating the patch-type piezoelectric driven mobile robot, comprising the following steps:

[0031] A first signal is applied to one side of the piezoelectric ceramic sheet of the patch piezoelectric transducer, and a second signal is applied to the other side of the piezoelectric ceramic sheet. The first signal and the second signal are π / 2 out of time, which causes the patch piezoelectric transducer to generate N-order bending vibration and N-1-order longitudinal vibration with a phase difference of π / 2 in time. This, in turn, causes the driving feet at the bottom of the two front end caps to generate clockwise micro-elliptical motions with the same direction. The two driving feet then drive the two axles to rotate in the same direction through friction, and the axles then drive the wheels to rotate in the same direction.

[0032] By changing the phase difference between the first and second signals in time to -π / 2, the particles on the plane of the driving foot at the bottom of the two front end caps are made to make a counterclockwise slight elliptical motion, thereby changing the direction of rotation of the axle and the wheel.

[0033] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0034] 1. It adopts a surface-mount piezoelectric drive, which has a greater driving force, higher dual-drive foot drive output efficiency, and a faster robot movement speed.

[0035] 2. The robot is open in design and does not require sealing, thus avoiding the problem of seal leakage under high water pressure.

[0036] 3. The drive foot plane contacts the wheel axle curved surface, avoiding the phenomenon of the drive foot and wheel axle getting stuck.

[0037] 4. Direct drive eliminates the need for a transmission mechanism, which is beneficial for lightweighting and miniaturization. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of a novel underwater robot based on a patch-type piezoelectric transducer according to the present invention;

[0039] Figure 2 This is a schematic diagram of the patch piezoelectric transducer of the present invention;

[0040] Figure 3 This is a schematic diagram of the piezoelectric ceramic sheet applying an electrical signal in the patch-type piezoelectric transducer of the present invention;

[0041] Figure 4 This is a schematic diagram of the structure of the substrate of the present invention;

[0042] Figure 5 This is a schematic diagram of the clamping structure of the present invention;

[0043] Figure 6 This is a schematic diagram of the axle structure of the present invention;

[0044] Figure 7 This is a schematic diagram of the structure of the wheel of the present invention;

[0045] Figure 8 This is a schematic diagram of the load-bearing box structure of the present invention;

[0046] Figure 9 This is a schematic diagram of the elliptical motion generated by the surface particles of the first and second driving feet of the patch piezoelectric transducer in this invention.

[0047] In the diagram, 1-Patch piezoelectric transducer, 1.1-Metal substrate, 1.2-Piezoelectric ceramic sheet, 1.3-Clamping beam, 1.4-Connecting beam, 1.5-First driving foot, 2-Substrate, 2.1-Oval hole, 2.2-Bearing hole, 2.3-Bolt hole, 3-Bolt, 4-Clamping structure, 4.1-Flange positioning hole, 4.2-Clamping structure boss, 5-Tension spring, 6-Pin, 7-First axle, 7.1-Pin hole, 7.2-Counterbolt hole, 7.3-Limiting surface, 8-Wheel, 8.1-Outer hub of the wheel, 8.2-Blade in the wheel, 8.3-Inner hub of the wheel, 9-Limiting gasket, 10-Second axle, 11-Bearing, 12-Load-bearing box, 12.1-Storage compartment, 12.2-Bolt hole. Detailed Implementation

[0048] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings:

[0049] This invention can be implemented in many different forms and should not be considered limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully express the scope of the invention to those skilled in the art. In the drawings, components are enlarged for clarity.

[0050] like Figure 1 As shown, this invention discloses a novel underwater robot based on a patch piezoelectric transducer, comprising a patch piezoelectric transducer, a clamping structure, a base, two tension springs, four bearings, a first axle, a second axle, four wheels, and two load-bearing boxes.

[0051] like Figure 2 As shown, the patch piezoelectric transducer includes a metal substrate, a piezoelectric ceramic sheet, a connecting beam, and a clamping beam.

[0052] The metal substrate includes a first vibrating beam, a second vibrating beam, a first driving foot, and a second driving foot.

[0053] The first and second vibration beams are two identical cuboids placed symmetrically from left to right. Each cuboid includes four sides (front, back, left, right) and two end faces (top and bottom). The first and second driving feet each include a driving end and a connecting end. The driving end is planar and the connecting end is planar. The connecting ends of the first and second driving feet are fixedly connected to the lower end faces of the first and second vibration beams, respectively.

[0054] The connecting beam is a symmetrical convex beam, which is set between the first vibrating beam and the second vibrating beam. The left and right end faces of the connecting beam are respectively fixed to the right end face of the first vibrating beam and the left end face of the second vibrating beam.

[0055] The clamping beam is a plate-shaped structure that is symmetrical about the center of the structure on both sides and protrudes in the middle. It is set between the first vibration beam and the second vibration beam. The left and right end faces of the clamping beam are fixed to the right end face of the first vibration beam and the left end face of the second vibration beam, respectively. Through holes are opened on the front and rear end faces of the protruding middle for clamping the patch piezoelectric transducer between the clamping structures.

[0056] The first and second vibration beams have piezoelectric ceramic sheets attached to their front and rear sides at the maximum amplitude of the Nth order bending vibration mode in the metal substrate, where N is an even number and is the bending vibration order of the pre-set working mode.

[0057] like Figure 3 As shown, the piezoelectric ceramic sheet used to generate bending vibration is polarized along its thickness direction; the piezoelectric ceramic sheet that generates bending vibration is polarized from the outer surface to the inner surface.

[0058] like Figure 5 As shown, the bottom of the clamping structure is a cuboid boss. Two upright plates are erected on the front and rear sides of the cuboid boss to clamp the piezoelectric transducer clamping beam. The two upright plates have through holes that are aligned with the through holes on the front and rear end faces of the piezoelectric transducer clamping beam. The left and right sides of the cuboid boss at the bottom of the clamping structure are locked between the first and second drive feet of the piezoelectric transducer to prevent the patch piezoelectric transducer from rotating during operation.

[0059] like Figure 4 As shown, the bottom of the base is a cuboid groove. The left and right side plates of the groove have concentric through holes for placing bearings and several bolt holes for placing bolts to facilitate suspension of the tension spring. The bottom has several through holes for limiting the propulsion device. There is a vertical plate on each side plate of the base, and the two vertical plates have waist-shaped holes for limiting the clamping structure.

[0060] Two tension springs are placed symmetrically on the outside of the two vertical plates of the base. One end of the tension spring is suspended on the bolt that passes through the waist hole on the two vertical plates of the base, and the other end is suspended on the bolt that is fixed to the bolt hole on the left and right side plates of the bottom groove of the base.

[0061] Four bearings are respectively installed in the bearing holes on the rectangular groove wall at the bottom of the base. The front and rear bearings are placed concentrically, and the inner holes of the left and right bearings are used to place the first wheel axle and the second wheel axle, respectively.

[0062] like Figure 6 As shown, the first and second wheel axles are respectively installed through the left and right bearing holes. The outer edge of the wheel axle is tangent to the driving foot plane at the bottom of the patch piezoelectric transducer. At the same time, the wheel axle is provided with pin holes on the outer side of the left and right bearing holes to place pins and limit the wheel axle. Meanwhile, the two ends of the wheel axle are stepped to connect with the inner hub of the wheel. Bolt holes are opened on both ends of the wheel axle to install bolts to limit the wheel along the wheel axle axis.

[0063] like Figure 7 As shown, the four wheels have identical structures. Each wheel includes an inner hub, an outer hub, a shaft, and several blades. The inner and outer hubs are concentrically arranged, with the inner hub having a waist-shaped hole and the outer hub having an annular shape. The blades are evenly installed between the inner and outer hubs, with one end of each blade fixed to the inner hub and the other end fixed to the outer hub. If combined with a buoyancy device to suspend the robot in water, the robot can swim in the water by rotating the blades. The axle is connected to the inner hub, and the wheel is fixed relative to the axle.

[0064] like Figure 8 As shown, the two load-bearing boxes have identical structures. Each load-bearing box consists of a rectangular base plate and four side plates that are vertically connected to the base plate. The four side plates and the base plate together form an open-top accommodating space, with one side plate extending out a connecting plate for connection to the base.

[0065] The four wheels are identical in shape and size, and the wheel axles and inner hubs are connected by an interference fit.

[0066] The axle and the base are fitted together by bearings.

[0067] The four wheels are exactly the same shape and size.

[0068] The first and second driving feet are identical in shape and size.

[0069] The two load-bearing boxes are exactly the same in shape and size.

[0070] The two vertical plates of the base are symmetrically arranged with equally spaced threaded holes for bolt engagement, which facilitates the adjustment of the extension of the tension spring.

[0071] One end of the tension spring is suspended on a bolt passing through the center hole of the flange, and the other end is suspended on bolts on the two vertical plates of the base.

[0072] The bearings are made of zirconia ceramic material to prevent them from rusting underwater and affecting the rotation of the wheel axle.

[0073] The present invention also discloses a method for operating the patch-type piezoelectric driven mobile robot, comprising the following steps:

[0074] like Figure 9 As shown, a first signal is applied to the piezoelectric ceramic sheet on one side of the patch piezoelectric transducer, and a second signal is applied to the piezoelectric ceramic sheet on the other side. The first signal and the second signal are π / 2 out of phase in time, causing the patch piezoelectric transducer to generate N-order bending vibration and N-1-order longitudinal vibration with a phase difference of π / 2 in time. This, in turn, causes the driving feet at the bottom of the two front end caps to generate clockwise micro-elliptical motions with the same direction. The two driving feet then drive the two axles to rotate in the same direction through friction, and the axles then drive the wheels to rotate in the same direction.

[0075] By changing the phase difference between the first and second signals in time to -π / 2, the particles on the plane of the driving foot at the bottom of the two front end caps are made to make a counterclockwise slight elliptical motion, thereby changing the direction of rotation of the axle and the wheel.

[0076] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0077] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A novel underwater robot based on a patch-type piezoelectric transducer, characterized in that, It includes a patch piezoelectric transducer, a clamping structure, a substrate, two tension springs, four bearings, a first axle, a second axle, four wheels, and two load-bearing boxes; The patch piezoelectric transducer includes a metal substrate, a connecting beam, and a clamping beam; The metal substrate includes a first vibrating beam, a second vibrating beam, a first driving foot, and a second driving foot; The first vibration beam and the second vibration beam are two identical cuboids placed symmetrically from left to right. Each cuboid includes four sides (front, back, left, right) and two end faces (top and bottom). The first driving foot and the second driving foot each include a driving end and a connecting end. The driving end is planar and the connecting end is planar. The connecting ends of the first driving foot and the second driving foot are fixedly connected to the lower end faces of the first vibration beam and the second vibration beam, respectively. The connecting beam is a symmetrical convex beam, which is set between the first vibrating beam and the second vibrating beam. The left and right end faces of the connecting beam are respectively fixed to the right end face of the first vibrating beam and the left end face of the second vibrating beam. The clamping beam is a plate-shaped structure that is symmetrical about the two sides of the structure center and protrudes in the middle. It is set between the first vibration beam and the second vibration beam. The left and right end faces of the clamping beam are fixed to the right end face of the first vibration beam and the left end face of the second vibration beam, respectively. Through holes are opened on the front and rear end faces of the protruding middle for clamping the patch piezoelectric transducer between the clamping structures. The first and second vibration beams have piezoelectric ceramic sheets attached to their front and rear sides at the maximum amplitude of the Nth order bending vibration mode in the metal substrate, where N is an even number and is the bending vibration order of the pre-set working mode. The piezoelectric ceramic sheet used to generate bending vibration is polarized along its thickness direction; the piezoelectric ceramic sheet that generates bending vibration is polarized from the outer side to the inner side. The bottom of the clamping structure is a cuboid boss. Two upright plates for clamping the piezoelectric transducer clamping beam are erected on the front and rear sides of the cuboid boss. The two upright plates have through holes that are aligned with the through holes on the front and rear end faces of the piezoelectric transducer clamping beam. The left and right sides of the cuboid boss at the bottom of the clamping structure are locked between the first and second driving feet of the piezoelectric transducer. The base has a rectangular groove at the bottom. The front and rear side plates of the groove have concentric through holes for placing bearings and several bolt holes for placing bolts to facilitate suspension of the tension spring. Several through holes are opened at the bottom for limiting the propulsion device. There is a vertical plate at the center of the front and rear side plates of the base. The two vertical plates have waist-shaped holes for limiting the clamping structure. The two tension springs are placed symmetrically on the outside of the two vertical plates of the base. One end of the tension spring is suspended on the bolt that passes through the waist hole on the two vertical plates of the base, and the other end is suspended on the bolt that is fixed to the bolt hole on the front and rear side plates of the bottom groove of the base. The four bearings are respectively installed in the bearing holes on the side plate of the cuboid groove at the bottom of the base. The front and rear bearings are placed concentrically, and the inner holes of the left and right bearings are respectively used to place the first wheel axle and the second wheel axle. The first and second axles are respectively installed through the left and right bearing holes. The outer edge of the axle is tangent to the driving foot plane at the bottom of the patch piezoelectric transducer. At the same time, the axle has pin holes on the outer side of the front and rear bearing holes to place pins and limit the bearings. The two ends of the axle are stepped to connect to the inner hub of the wheel. Bolt holes are opened on both ends of the axle to install bolts to limit the wheel along the axle axis. The four wheels have identical structures. Each wheel includes an inner hub, an outer hub, a shaft, and several blades. The inner and outer hubs are concentrically arranged, with the inner hub having a waist-shaped hole and the outer hub having an annular shape. The blades are evenly installed between the inner and outer hubs, with one end of each blade fixedly connected to the inner hub and the other end fixedly connected to the outer hub. The axle is connected to the inner hub, and the wheel is fixed relative to the axle. The two load-bearing boxes have identical structures. Each load-bearing box consists of a rectangular base plate and four side plates that are vertically connected to the base plate. The four side plates and the base plate together form an open-top accommodating space, with one side plate extending out a connecting plate for connection to the base.

2. The patch-type piezoelectric transducer underwater robot according to claim 1, characterized in that, The four wheels are rotatably connected by an interference fit between the axle and the inner hub.

3. The patch-type piezoelectric transducer underwater robot according to claim 1, characterized in that, The axle and the base are fitted together by bearings.

4. The patch-type piezoelectric transducer underwater robot according to claim 1, characterized in that, The four wheels are identical in shape and size.

5. The patch-type piezoelectric transducer underwater robot according to claim 1, characterized in that, The first and second driving feet are identical in shape and size.

6. The patch-type piezoelectric transducer underwater robot according to claim 1, characterized in that, The two load-bearing boxes are exactly the same in shape and size.

7. The patch-type piezoelectric transducer underwater robot according to claim 1, characterized in that, The two vertical plates of the base have symmetrically arranged threaded holes at equal intervals for use with bolts.

8. The patch-type piezoelectric transducer underwater robot according to claim 1 or 7, characterized in that, One end of the tension spring is suspended on a bolt passing through the center hole of the flange, and the other end is suspended on bolts on the two vertical plates of the base.

9. The patch-type piezoelectric transducer underwater robot according to claim 1, characterized in that, The bearing is made of zirconia ceramic material.

10. The working method of an underwater robot based on the patch-type piezoelectric transducer according to claim 1, characterized in that, Includes the following processes: A first signal is applied to one side of the piezoelectric ceramic sheet of the patch piezoelectric transducer, and a second signal is applied to the other side of the piezoelectric ceramic sheet. The first signal and the second signal are π / 2 out of time, which causes the patch piezoelectric transducer to generate N-order bending vibration and N-1-order longitudinal vibration with a phase difference of π / 2 in time. This, in turn, causes the driving feet at the bottom of the two front end caps to generate clockwise micro-elliptical motions with the same direction. The two driving feet then drive the two axles to rotate in the same direction through friction, and the axles then drive the wheels to rotate in the same direction. By changing the phase difference between the first and second signals in time to -π / 2, the particles on the plane of the driving foot at the bottom of the two front end caps are made to make a counterclockwise slight elliptical motion, thereby changing the direction of rotation of the axle and the wheel.

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