Lightweight and compact lunar regolith sampling system mountable on rover

Abstract

A lightweight and compact lunar regolith sampling system mountable on a rover. The system comprises a three-degree-of-freedom manipulator based on open cylindrical thin-shell rods, and a control unit based on three-dimensional force / torque information, wherein the three-degree-of-freedom manipulator based on the open cylindrical thin-shell rods has a translation mechanism (1), a lateral rotation mechanism (2) and a rear rotation mechanism (3), and the lower part of the three-degree-of-freedom manipulator is connected to a sensor (4) and a sampler (5); and the control unit based on the three-dimensional force / torque information collects force sensing information and sends the force sensing information to an NUC, and the NUC reads the position of an output shaft of a servo electric motor by means of CAN bus communication, generates a real-time control instruction on the basis of a compliant control algorithm, and sends the real-time control instruction to the servo electric motor by means of CAN bus communication, so as to realize closed-loop control. The system has lightweight characteristics and a strong storage capacity while ensuring the structural strength, uses three-dimensional force / torque information to monitor an operation environment and adjusts a sampling strategy in real time, thereby effectively handling complex operation environments and thus significantly improving the safety and flexibility of sampling operations.

Description

A lightweight lunar soil sampling system that can be carried on a rover Technical Field

[0001] The present invention belongs to the technical field of deep space exploration equipment, and specifically relates to a lightweight and compact lunar soil sampling system that can be carried on a rover. Background Art

[0002] Lunar exploration has become a key mission in exploring major scientific questions, such as the formation and evolution of the universe and the origin of life. Unmanned lunar probes, including landers and rovers, are the primary means of sampling the lunar surface. Traditional lunar soil sampling techniques, such as the unmanned lander sampling schemes of the United States and the Soviet Union, are limited in scope and flexibility, and no successful sampling projects have been reported in recent years. Although the Chang'e-5 mission achieved breakthroughs in lunar soil sampling, its focus was on point-by-point sampling around the lander, which limited the sampling area and resulted in poor sample diversity. Rovers, on the other hand, can explore larger areas by moving across the surface of celestial bodies. Equipped with a sampling system, they have the ability to collect samples from various locations, providing more comprehensive data and enabling more extensive scientific research.

[0003] The rover relies primarily on solar power, and the lunar surface environment to be explored is unknown and complex, requiring a lightweight and compact sampling system with environmental monitoring capabilities. Typical existing sampling system designs include a rigid robotic arm and its end-cap sampling mechanism, sampling planning based on visual monitoring, and a sampling process based on open-loop motion control. However, faced with the unknown operating environment and complex lunar surface conditions, the rigid robotic arm is heavy, increasing the rover's load; visual monitoring cannot effectively detect the conditions beneath the lunar soil and lacks environmental perception; and open-loop control strategies cannot adjust the sampling trajectory in real time to cope with the changing operating environment, which can easily cause structural damage.

[0004] In view of the problems such as the heavy rigid structure of the existing sampling system, the inability of visual monitoring to perceive the working environment under the lunar soil, and the inability of the open-loop motion control scheme to adjust the sampling trajectory in real time according to the environment, it is necessary to develop a lightweight lunar soil sampling system that can be carried on the rover.

[0005] Summary of the Invention

[0006] To solve the above problems, the present invention discloses a lightweight and compact lunar soil sampling system that can be carried on a rover. It has lightweight characteristics and strong storage capacity while ensuring structural strength. It uses three-dimensional force / torque information to monitor the working environment and adjust the sampling strategy in real time, effectively coping with complex working environments and significantly improving the safety and flexibility of sampling operations.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] A lightweight and compact lunar soil sampling system that can be carried on a rover includes a three-degree-of-freedom robotic arm based on an open cylindrical thin-shell rod and a control unit based on three-dimensional force / torque information.

[0009] The three-degree-of-freedom robotic arm based on the open cylindrical thin shell rod has a translation mechanism, a side rotation mechanism, and a rear rotation mechanism, which respectively provide the sampler with up and down movement and left and right, front and back swing functions, and the sensor and sampler are connected at the bottom;

[0010] The translation mechanism is composed of a pair of open cylindrical thin shell rods, two sets of concave and convex roller pairs, a pair of storage boxes, a bevel gear set, a housing and a servo motor. The translation movement of the sampler can be achieved by shrinking the thin shell rods.

[0011] The open cylindrical thin shell rod is a coil spring type retractable flexible arm made of spring steel, installed in the storage box, with an array of equidistant circular through holes obtained by laser cutting on its surface, extending downward through the small opening at the bottom of the shell;

[0012] The concave and convex roller pair has the same arc surface as the open cylindrical thin shell rod, wherein the central circumference of the convex roller is the tooth surface, distributed with equidistant cylindrical small teeth, the tooth pitch is consistent with the hole pitch on the surface of the open cylindrical thin shell rod, and the central circumference of the concave roller is the groove surface, the groove surface depth is consistent with the height of the small teeth;

[0013] The concave and convex roller pairs are symmetrically fixed to the support inside the shell through bearings and are distributed on both sides of the open cylindrical thin shell rod. The rod surface is pressed by adjusting the distance between the concave and convex rollers, and the small teeth on the central circumference of the convex roller engage with the rod surface.

[0014] The storage boxes, a pair in total, are symmetrically fixed on the upper part of the inner portion of the shell;

[0015] The bevel gear set is fixed to the outside of the housing and comprises a pair of parallel bevel gears in the vertical direction, a pair of collinear bevel gears in the horizontal direction and the optical axis, wherein the horizontal collinear bevel gears are symmetrically connected in series on the optical axis and mesh with the parallel bevel gears to achieve the rotation linkage of the bevel gear set, and the parallel bevel gears are fixed to the external wheel shafts of the two cam rollers through a coupling to achieve the joint rotation movement of the two cam rollers;

[0016] The housing has a rotating shaft protruding outward on the side surface and is fixed to the rear rotating mechanism;

[0017] The two rotating mechanisms, one providing a forward and backward swing function and the other providing a left and right swing function, each comprise a servo motor and a motor box;

[0018] The side rotation mechanism, the side motor box as the rotating blade, encapsulates the servo motor, and the side servo motor output shaft is fixed to the side rotation shaft of the translation mechanism housing;

[0019] The rear rotation mechanism, the rear servo motor output shaft and the side motor box of the side rotation mechanism are fixed through a coupling, and the axial direction is perpendicular to the axial direction of the side rotation mechanism. The body of the rear servo motor is fixed in the rear motor box, and the rear motor box can also be installed on the patrol vehicle body as the end of the mechanical arm;

[0020] The sensor uses a three-dimensional force / torque sensor to monitor the Z-axis force Fz and the X- and Y-axis moments Mx and My. It is installed at the end of the translation joint, where the Z axis is collinear with the movement direction of the translation joint, and the X and Y axes are parallel to the rotation axes of the side rotation mechanism and the rear rotation mechanism respectively;

[0021] The sampler is a small drill or excavation sampler suitable for shallow lunar soil sampling tasks;

[0022] The control unit based on three-dimensional force / torque information is composed of a data acquisition card and a microcomputer NUC. The data acquisition card collects force information fed back by the three-dimensional force / torque sensor and sends it to the microcomputer NUC via serial communication. The microcomputer NUC reads the three-dimensional force / torque information transmitted by the data acquisition card via serial communication, uses CAN bus communication to read the output shaft position of the servo motor, generates real-time control instructions in combination with a compliant control algorithm, and sends them to the servo motor via CAN bus communication to realize a closed-loop control.

[0023] The compliant control algorithm includes the following control process:

[0024] S1: The microcomputer NUC reads the three-dimensional force / torque sensor information through the data acquisition card and obtains the usable external force vector after low-pass filtering: F e =[F z M x M y ];

[0025] S2: The damping-mass admittance control model without stiffness term is selected as the motion equation, and compliant control is performed in the joint space, where θ r is the reference position vector defined before the mission, B and K are the three-dimensional damping and mass coefficient matrices respectively, θ d is the desired position vector of the servo motor in the joint coordinate system, E θ is the compliant deviation, s is the differential operator: F e =(Ms 2 +Bs)(θ r -θ d ) E θ =θ r -θ d E θ =F e / (Ms 2 +Bs)

[0026] S3: Run the above model in the microcomputer NUC to obtain the real-time desired motor angle vector θ d =[θ z θ x θ y ], where θ z ,θ x ,θ y As the target angle, it is transmitted to the servo motors in the translation mechanism, side rotation mechanism, and rear rotation mechanism through CAN bus communication to complete motion control.

[0027] The beneficial effects of the present invention are:

[0028] (1) The lightweight lunar soil sampling system designed by the present invention, which can be carried on a rover, uses a double-open cylindrical thin shell rod as a flexible translation mechanism. It has the advantages of a large extension stroke and high axial strength. It is small in size and light in weight, which makes it easy to carry on the rover to carry out sampling work, greatly reducing the transportation cost.

[0029] (2) The lightweight lunar soil sampling system designed by the present invention can be carried on a rover. The system structure has two degrees of freedom joints, namely, forward and backward swing freedom and left and right swing freedom, and a linear translation joint. It has a compact design, a small size, and a large and flexible movement space.

[0030] (3) The lightweight lunar soil sampling system designed by the present invention, which can be carried on a rover, uses a three-dimensional force / torque sensor to accurately obtain multi-dimensional force signals during the sampling process in real time, thereby realizing the monitoring of the operating status of the system under the lunar soil.

[0031] (4) The lightweight lunar soil sampling system designed by the present invention, which can be carried on a rover, uses a damping-mass admittance control model without stiffness terms as the motion equation. It flexibly avoids external obstacles through posture adjustment, avoids damage to the mechanism, and improves the environmental adaptability of the system.

[0032] (5) The lightweight lunar soil sampling system designed by the present invention can be carried on a rover. The movement direction of the mechanism corresponds one-to-one with the monitored force direction, and closed-loop control is performed in the joint space. The algorithm is stable and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG1 is a schematic diagram of the device of the present invention.

[0034] FIG2 is a schematic diagram of the translation mechanism of the present invention.

[0035] FIG3 is a schematic diagram of a concave-convex gear pair according to the present invention.

[0036] FIG4 is a schematic diagram of a bevel gear set according to the present invention.

[0037] FIG5 is a schematic diagram of the rotating mechanism of the present invention.

[0038] FIG6 is a schematic diagram of the control process of the present invention.

[0039] List of Figure Symbols:

[0040] 1. Translation mechanism, 2. Side rotation mechanism, 3. Rear rotation mechanism, 4. Sensor, 5. Sampler, 11. Storage box, 12. Thin shell rod, 13. Concave and convex roller pair, 14. Bevel gear set, 15. Housing, 131. Cylindrical small teeth, 132. Groove surface, 133. Bearing, 134. Support, 141. Parallel bevel gear, 142. Collinear bevel gear, 143. Optical axis, 21. Side motor box, 22. Side servo motor output shaft, 31. Rear servo motor output shaft, 32. Rear front and rear motor box. DETAILED DESCRIPTION

[0041] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0042] The present invention proposes a lightweight and compact lunar soil sampling system that can be carried on a rover, including a three-degree-of-freedom robotic arm based on an open cylindrical thin-shell rod and a control unit based on three-dimensional force / torque information.

[0043] As shown in Figure 1, the three-degree-of-freedom robotic arm based on an open cylindrical shell rod has a translation mechanism 1, a side rotation mechanism 2, and a rear rotation mechanism 3, which respectively provide the sampler with up and down movement and left and right, front and back swing functions. The sensor 4 and sampler 5 are connected at the bottom.

[0044] As shown in FIG2 , the translation mechanism 1 is composed of a pair of storage boxes 11, a pair of open cylindrical thin shell rods 12, two sets of concave and convex roller pairs 13, a bevel gear set 14 and a housing 15. A servo motor under position control is used as a driving device. The output shaft of the servo motor is fixed to the internal rotating shaft of one of the convex rollers through a coupling, and its body is fixed inside the housing 15. The translation movement of the sampler 5 can be achieved by driving the contraction of the thin shell rods 12.

[0045] The storage boxes 11, a pair in total, are symmetrically fixed above the interior of the housing 15 and are used to limit and store the open cylindrical thin shell rods 12;

[0046] The open cylindrical thin shell rod 12 is a coil spring type retractable flexible arm made of spring steel, characterized by high axial rigidity and small retracted volume. It is installed in the storage box 11 and extends downward through the small opening below the shell 15. The surface has an array of equidistant circular through holes obtained by laser cutting.

[0047] As shown in FIG3 , the concave-convex roller pair 13 has the same arc surface as the open cylindrical thin shell rod, wherein the central circumference of the convex roller is a tooth surface, distributed with equidistant cylindrical small teeth 131, the tooth pitch is consistent with the hole pitch on the surface of the open cylindrical thin shell rod, the central circumference of the concave roller is a groove surface 132, the groove surface depth is consistent with the small tooth height, and both are symmetrically fixed on the internal support 134 of the shell through bearings 133, distributed on both sides of the open cylindrical thin shell rod, and the rod surface is pressed by adjusting the distance between the concave-convex rollers, and the small teeth on the central circumference of the convex roller are engaged with the rod hole surface;

[0048] As shown in FIG4 , the bevel gear set 14 is fixed to the outside of the housing and comprises a pair of parallel bevel gears 141 in the vertical direction, a pair of collinear bevel gears 142 in the horizontal direction, and an optical axis 143. The horizontal collinear bevel gears are symmetrically connected in series on the optical axis and mesh with the parallel bevel gears to achieve the rotation linkage of the bevel gear set. The parallel bevel gears are fixed to the external axles of the two cam rollers via a coupling to achieve the joint rotation motion of the two cam rollers.

[0049] The housing 15 has a rotating shaft protruding outward on the side surface, which is fixed to the rear rotating mechanism 2;

[0050] As shown in FIG5 , the two rotating mechanisms 2 and 3 , the rotating mechanism 2 providing the forward and backward swing function and the rotating mechanism 3 providing the left and right swing function, both include a servo motor and a motor box;

[0051] The side rotation mechanism 2, the side motor box 21 as the rotating blade, encapsulates the servo motor, the side servo motor output shaft 22 is fixed to the side shaft of the translation mechanism housing 15;

[0052] The rear rotation mechanism 3, the rear servo motor output shaft 31 and the side motor box 21 of the side rotation mechanism 2 are fixed through a coupling, and the axial direction is perpendicular to the axial direction of the side rotation mechanism 2. The body of the rear rotation mechanism 3 is fixed in the rear motor box 32, and the rear motor box 32 can also be installed on the patrol vehicle body as the end of the mechanical arm;

[0053] The sensor 4 is a three-dimensional force / torque sensor that monitors the Z-axis force Fz and the X- and Y-axis moments Mx and My. It is installed at the end of the translation joint, where the Z axis is collinear with the movement direction of the translation joint, and the X and Y axes are parallel to the rotation axes of the side rotation mechanism and the rear rotation mechanism respectively;

[0054] The sampler 5 is a small drill or excavation sampler suitable for shallow lunar soil sampling tasks;

[0055] As shown in Figure 6, the control unit based on three-dimensional force / torque information is composed of a data acquisition card and a microcomputer NUC. The data acquisition card collects the force information fed back by the three-dimensional force / torque sensor and sends it to the microcomputer NUC through serial communication. The microcomputer NUC reads the three-dimensional force / torque information transmitted by the data acquisition card through serial communication, uses CAN bus communication to read the output shaft position of the servo motor, generates real-time control instructions in combination with the compliant control algorithm, and sends them to the servo motor through CAN bus communication to realize a closed-loop control.

[0056] The compliant control algorithm includes the following control process:

[0057] S1: The microcomputer NUC reads the three-dimensional force / torque sensor information through the data acquisition card and obtains the usable external force vector after low-pass filtering: F e =[F z M x M y ];

[0058] S2: The damping-mass admittance control model without stiffness term is selected as the motion equation, and compliant control is performed in the joint space, where θ r is the reference position vector defined before the mission, B and K are the three-dimensional damping and mass coefficient matrices respectively, θ d is the desired position vector of the servo motor in the joint coordinate system, E θ is the compliant deviation, s is the differential operator: F e =(Ms 2 +Bs)(θ r -θ d ) E θ =θ r -θ d E θ =F e / (Ms 2 +Bs)

[0059] S3: Run the above model in the microcomputer NUC to obtain the real-time desired motor angle vector θ d =[θ z θ x θ y ], where θ z ,θ x ,θ y As the target angle, it is transmitted to the servo motors in the translation mechanism, side rotation mechanism, and rear rotation mechanism through CAN bus communication to complete motion control, achieve the movement effect of avoiding the resistance in the direction and realize environmental adaptation.

[0060] It should be noted that the above content merely illustrates the technical idea of ​​the present invention and cannot be used to limit the scope of protection of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications all fall within the scope of protection of the claims of the present invention.

Claims

1. A lightweight lunar soil sampling system that can be carried on a rover, characterized by: It includes a three-degree-of-freedom manipulator based on an open cylindrical shell rod and a control unit based on three-dimensional force / torque information; The three-degree-of-freedom robotic arm based on the open cylindrical thin shell rod has a translation mechanism (1), a side rotation mechanism (2), and a rear rotation mechanism (3), which respectively provide the sampler with up and down movement and left and right, front and back swing functions, and is connected to a sensor (4) and a sampler (5) at the bottom; The control unit based on three-dimensional force / torque information is composed of a data acquisition card and a microcomputer NUC. The data acquisition card collects force information fed back by the three-dimensional force / torque sensor and sends it to the microcomputer NUC through serial communication. The microcomputer NUC reads the three-dimensional force / torque information transmitted by the data acquisition card through serial communication, uses CAN bus communication to read the output shaft position of the servo motor, generates real-time control instructions in combination with the flexible control algorithm, and sends them to the servo motor through CAN bus communication to realize a closed-loop control.

2. The lightweight lunar soil sampling system that can be carried on a rover according to claim 1 is characterized by: The translation mechanism (1) is composed of a pair of storage boxes (11), a pair of open cylindrical thin shell rods (12), two sets of concave and convex roller pairs (13), a bevel gear set (14) and a shell (15). A servo motor under position control is used as a driving device. The output shaft of the servo motor is fixed to the internal rotating shaft of one of the convex rollers through a coupling. The body of the servo motor is fixed inside the shell (15). The translation movement of the sampler (5) is achieved by driving the contraction of the thin shell rods (12). The storage boxes (11), a pair in total, are symmetrically fixed above the interior of the housing (15) and are used to limit and store the open cylindrical thin shell rods (12); The open cylindrical thin shell rod (12) is a coil spring type retractable flexible arm made of spring steel, installed in the storage box (11), extending downward through the small opening below the shell (15), and having an array of equidistant circular through holes obtained by laser cutting on its surface; The concave-convex roller pair (13) has the same arc surface as the open cylindrical thin shell rod, wherein the central circumference of the convex roller is a tooth surface, distributed with equidistant cylindrical small teeth (131), the tooth pitch is consistent with the hole pitch on the surface of the open cylindrical thin shell rod, the central circumference of the concave roller is a groove surface (132), the groove surface depth is consistent with the small tooth height, and both are symmetrically fixed on the internal support (134) of the shell through bearings (133), distributed on both sides of the open cylindrical thin shell rod, and the rod surface is pressed by adjusting the distance between the concave-convex rollers, and the small teeth on the central circumference of the convex roller are engaged with the rod hole surface; The bevel gear set (14) is fixed to the outside of the housing and comprises a pair of parallel bevel gears (141) in the vertical direction, a pair of collinear bevel gears (142) in the horizontal direction and an optical axis (143), wherein the collinear bevel gears in the horizontal direction are symmetrically connected in series on the optical axis and mesh with the parallel bevel gears to realize the rotation linkage of the bevel gear set, and the parallel bevel gears are fixed to the external wheel shafts of the two convex rollers through a coupling to realize the joint rotation movement of the two convex rollers; The housing (15) has a rotating shaft protruding outward on its side surface and is fixed to the rear rotating mechanism (2).

3. The lightweight lunar soil sampling system capable of being carried on a rover according to claim 1 is characterized in that: Two rotating mechanisms (2) and (3), one of which provides a forward and backward swinging function and the other provides a left and right swinging function, each including a servo motor and a motor box; The side rotating mechanism (2) has a side motor box (21) as a rotating blade, which is encapsulated with a servo motor, and a side servo motor output shaft (22) is fixed to the side rotating shaft of the translation mechanism housing (15); The rear rotation mechanism (3), the rear servo motor output shaft (31) and the side motor box (21) of the side rotation mechanism (2) are fixed through a coupling, and the axial direction is perpendicular to the axial direction of the side rotation mechanism (2). The body of the rear rotation mechanism (3) is fixed in the rear motor box (32), and the rear motor box (32) is also installed on the patrol vehicle body as the end of the mechanical arm.

4. The lightweight lunar soil sampling system capable of being carried on a rover according to claim 1, characterized in that: The sensor (4) adopts a three-dimensional force / torque sensor to monitor the Z-axis force Fz and the X-axis and Y-axis moments Mx and My, and is installed at the end of the translation joint, wherein the Z axis is collinear with the movement direction of the translation joint, and the X and Y axes are parallel to the rotation axes of the side rotation mechanism and the rear rotation mechanism respectively.

5. The lightweight lunar soil sampling system capable of being carried on a rover according to claim 1 is characterized in that: The sampler (5) is a small drilling or digging sampler suitable for shallow lunar soil sampling tasks.

6. The lightweight lunar soil sampling system capable of being carried on a rover according to claim 1 is characterized in that: The compliant control algorithm includes the following control process: S1: The microcomputer NUC reads the 3D force / torque sensor information through the data acquisition card and obtains the external force vector after low-pass filtering: F e =[F z M x M y ]; S2: The damping-mass admittance control model without stiffness term is selected as the motion equation, and compliant control is performed in the joint space, where θ r is the reference position vector defined before the mission, B and K are the three-dimensional damping and mass coefficient matrices respectively, θ d is the desired position vector of the servo motor in the joint coordinate system, E θ is the compliant deviation, and s is the differential operator: F e =(Ms 2 +Bs)(θ r -θ d ) E θ =θ r -θ d E θ =F e / (Ms 2 +Bs) S3: Run the above model in the microcomputer NUC to obtain the real-time desired motor angle vector θ d =[θ z θ x θ y ], where θ z ,θ x ,θ y As the target angle, it is transmitted to the servo motors in the translation mechanism, side rotation mechanism, and rear rotation mechanism through CAN bus communication to complete motion control, achieve the motion effect of avoiding the resistance in the direction and realize environmental adaptation.

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