Robot foot-end multi-dimensional force detection method and foot-end device based on crack sensor

Abstract

The present invention relates to a robot foot-end multi-dimensional force detection method and foot-end device based on a crack sensor, which includes the following steps: step one: installing a crack sensor at the robot foot-end to detect the external force; step two: determining the force applied to the foot-end according to the external force detected by the crack sensor; step three: calculating the force direction of the foot-end, and judging whether the foot-end is slipping, and adjusting the robot's gait; step four: determining the multi-dimensional force applied to the robot foot-end. The present invention converts the change of force into the change of voltage signal through the crack sensor, constructs a foot-end multi-dimensional force detection method by analyzing the foot-end force model, realizes the real-time detection of the robot's ground contact force, and the detection result is accurate and reliable; the foot-end device proposed by the present invention can adapt to robot calf structures of various structural forms by changing the radius of the base, and can quickly install the entire device. The device has a reasonable structure and improves the universality of the detection device.

Description

Technical Field

[0001] The present application relates to the technical field of robot motion control and force sensors, and in particular to a robot foot-end multi-dimensional force detection method and foot-end device based on a crack sensor. Background Art

[0002] Robots are usually used in dangerous environments to perform tasks instead of humans. Compared with wheeled and tracked robots, legged robots have better adaptability in complex unstructured environments such as beaches, jungles, snow, and grasslands. In recent years, they have become a research hotspot in various countries.

[0003] During the actual movement of the robot, the foot end is constantly in contact with the ground to produce collisions and impacts. Real-time and accurate detection of the actual force on the foot end during the movement is the basis for the robot to achieve various motion control strategies such as compliant control, contact force control and CPG control. In order to detect the force on the robot foot end, there are usually two ways to classify the force sensor installation method: installing the multi-dimensional force sensor on the front of the robot leg foot end and installing the uniaxial force sensor on the driving joint of the foot robot. For a foot robot that applies all loads and impacts to the foot, it is a considerable burden to install the multi-dimensional force sensor on the front of the robot leg foot end to directly detect the interaction force. This installation method has very high requirements on the manufacturing process and tolerance of the sensor. Therefore, the price of this type of force sensor is often high; installing the uniaxial force sensor on the driving joint of the foot robot to detect the foot end force requires combining the inverse dynamics and statics equations of the robot leg to indirectly solve the foot end force of the robot. However, due to the accuracy of the inverse dynamics model and the uncertainty of friction, the foot end force obtained by this method is often inaccurate. In general, the force sensors installed on the robot's legs have many problems, such as high price, inability to directly detect changes in the foot-end force, signal delay and vibration. Since the contact force during the foot-ground interaction of the robot is uncontrollable, in order to avoid damage to the force detection capability of the foot-end device due to large impact forces, the foot-end device should have a certain overload protection capability. Therefore, it is necessary to design a foot-end device that can directly detect changes in the multi-dimensional force at the foot-end, is low-cost, and has an overload protection function.

[0004] After millions of years of evolution, the morphological structure of scorpions has not changed significantly. They have evolved sharp seam receptors on their body surface, which are very sensitive to stress and strain signals. The present invention imitates the seam receptor structure of scorpions and designs a foot-end device of a legged robot based on the seam receptor of scorpions. This structure is of great significance for ensuring the good adaptability and movement stability of the legged robot in unknown unstructured environments. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention converts the change of force into the change of voltage signal through a crack sensor, determines the foot-end multi-dimensional force detection method by analyzing the foot-end force model, realizes the real-time detection of the robot's ground contact force, and the detection result is accurate and reliable; the foot-end device proposed in the present invention can adapt to various structural forms of robot calf structures by changing the radius of the base, and the overall device can be quickly installed, the structure is reasonable, and the universality of the detection device is improved.

[0006] To achieve the above purpose, the solution adopted by the present invention is:

[0007] A robot foot end multi-dimensional force detection method based on crack sensor, comprising the following steps:

[0008] Step 1: Install a crack sensor at the foot of the robot to detect the external force;

[0009] The three crack sensors are installed on the foot ends of the robot respectively. When the outer surface of the foot end is subjected to force, the inner surface of the foot end is closely fitted with the crack sensor, so that the crack sensor is deformed by force, and the resistance value increases. The resistance change is converted into an electrical signal of voltage output through the measurement circuit; the sensing signals of the three crack sensors are U1, U2 and U3, and the three sensing signals are proportional to their respective forces F1, F2, F3, as shown below:

[0010]

[0011] Where: F1, F2 and F3 are the external forces detected by the first, second and third crack sensors respectively; U1, U2 and U3 are the voltage output signals of the first, second and third crack sensors respectively; K represents the voltage-force conversion coefficient;

[0012] Step 2: Determine the force applied to the foot end according to the external force detected by the crack sensor;

[0013] Obtain the forces detected by the three crack sensors in step 1. The method for obtaining the forces acting on the foot end is as follows:

[0014]

[0015] Where: F t Indicates the force acting on the foot end; F x 、F y and F z Respectively represent the component forces in the directions of the x-axis, y-axis, and z-axis of the world coordinate system;

[0016] Step 3: Calculate the force direction of the foot end, determine whether the foot end is slipping, and adjust the robot gait;

[0017] Step 31: Calculate the angle between the force on the foot end and the horizontal ground to determine the force direction on the foot end;

[0018] When the force F t When acting on the surface of the foot end, a unique corresponding voltage is obtained, and the following set of equations is constructed to solve the force on the surface of the foot end;

[0019]

[0020] Then according to the magnitude of the three components, we can solve for F t The angle θ with the horizontal ground; according to F x and F y Solve for F t The angle ψ between the projection on the XY plane and the X-axis direction is as follows:

[0021]

[0022] Where: θ represents the angle between the foot force and the horizontal ground; ψ represents the angle between the foot force projected onto the horizontal ground and the X-axis direction;

[0023] Step 32: According to the force on the foot end and the angle between the force and the horizontal ground, determine whether the foot end is slipping, and adjust the robot gait;

[0024] According to the force on the foot end, the actual internal friction angle of the friction cone constraint is determined to further determine whether the foot end is slipping; the method for obtaining the internal friction angle is as follows:

[0025]

[0026] Where: θ z represents the internal friction angle of the friction cone constraint;

[0027] Step 4: Determine the multi-dimensional forces acting on the robot foot;

[0028] According to the force on the foot end calculated in step 2 and the angle between the force on the foot end and the horizontal ground calculated in step 3, the multi-dimensional force on the foot end of the robot can be determined.

[0029] Preferably, in step 1, the three crack sensors are respectively installed on the foot ends of the robot, specifically: the three crack strain sensors are arranged at intervals of 120°, surrounding the foot ends, and the inclination of the sensor slots on the base is 45°.

[0030] Preferably, in step 1, according to the force applied to the foot end, the actual internal friction angle of the friction cone constraint is determined to further determine whether the foot end is slipping, specifically:

[0031] When the robot foot is in a swinging state, the reaction force F tis 0; then the vertical amplitude of the plantar reaction force is limited to the component force F in the direction of the z-axis of the world coordinate system z To ensure that there is no relative sliding between the sole of the foot and the ground, the horizontal component of the sole reaction force cannot be greater than the product of its vertical component and the sliding friction coefficient μ, that is, the friction cone condition is satisfied, as shown below:

[0032]

[0033] Where: μ represents the sliding friction coefficient;

[0034] Split the above equation into 4 linear constraints, and then combine them with the setting condition F z ≤5000N, a total of 5 linear constraints, the plantar reaction force constraints are integrated into a matrix, and the solution equations constructed by the ground friction coefficient μ are as follows:

[0035]

[0036] According to the ground sliding friction coefficient μ, the maximum internal friction angle of the friction cone can be calculated as follows;

[0037] θ max =arctanμ;

[0038] Where: θ max represents the maximum internal friction angle of the friction cone;

[0039] Then, according to the friction cone constraint calculated in step 32, the actual internal friction angle θ z Make a judgment; if the calculated friction cone constrains the actual internal friction angle θ z Smaller than the maximum internal friction angle θ of the friction cone max , the foot end does not slip; otherwise, the foot end slips. At this time, it is necessary to adjust the robot's gait and reduce the robot's stride to ensure the robot's stable motion state.

[0040] The second aspect of the present invention provides a foot-end device of a robot foot-end multi-dimensional force detection method based on the aforementioned crack sensor, which includes a foot-end, a baffle, a crack sensor, a base and a pre-tightening bolt;

[0041] The foot end is a spherical structure capable of contacting the ground from all directions;

[0042] The baffle is capable of fixing the foot end and three crack sensors;

[0043] The crack sensor comprises a sensor base, a sensor body, a sensor cover and a sensor slot; the crack sensor is placed in the base and connected to the sensor base; the sensor body is placed in the sensor slot with rigidity, and the sensor cover is attached to the upper and lower surfaces of the sensor slot;

[0044] The pre-tightening bolt is used to fix the foot end and provide calibration and zeroing for the crack sensor. After the crack sensor is installed on the robot leg, the pre-tightening screw is added to the base of the foot end.

[0045] Preferably, the crack sensor is a crack strain sensor, the main body of the crack strain sensor is an elastomer, and the lower surface of the elastomer is provided with multiple groups of parallel lyre-shaped cracks that can change when subjected to force. Changes in the length of the lyre-shaped cracks affect the resistance value, thereby causing the voltage of the crack strain sensor to change.

[0046] Preferably, an arc groove is provided in the sensor base to enable the crack strain sensor to deform and limit the degree of deformation.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) The foot-end multi-dimensional force detection method proposed in the present invention converts the force change into the voltage signal change through the crack sensor, and determines the multi-dimensional force on the foot-end by analyzing the foot-end force model, thereby realizing the real-time detection of the robot's ground contact force, and the detection result is accurate and reliable;

[0049] (2) The foot-end multi-dimensional force detection device proposed by the present invention adds a pre-tightening screw to the base of the foot-end sensor, which not only fixes the foot end, but also provides a convenient and quick calibration and zeroing method for the foot-end force sensor, and has an overload protection function;

[0050] (3) The size of the foot-end device proposed in the present invention is mainly based on the size of the base. By changing the radius of the base, it can be adapted to robot calf structures of various structural forms, and the entire device can be quickly installed. The structure of this device is reasonable, which improves the universality of the detection device. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a control block diagram of the robot foot end multi-dimensional force detection method based on crack sensor of the present invention;

[0052] Figure 2 It is a simplified diagram of the force on the foot end of the present invention;

[0053] Figure 3 It is a structural diagram of a crack sensor of the foot-end device of the present invention;

[0054] Figure 4 This is an axonometric diagram of the crack strain sensor of the present invention;

[0055] Figure 5 It is a front view of the crack strain sensor of the present invention;

[0056] Figure 6 This is a force simulation diagram of the foot end of the present invention;

[0057] Figure 7 It is a spatial schematic diagram of the force direction of the foot end of the present invention.

[0058] Main reference numerals:

[0059] 1. Foot end; 2. Baffle; 3. Crack sensor; 4. Base; 5. Pre-tightening bolts; 6. Sensor cover; 7. Sensor body; 8. Sensor slot; 9. Sensor base. DETAILED DESCRIPTION

[0060] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0061] The foot-end multi-dimensional force detection method proposed in the embodiment of the present invention converts the force change into the voltage signal change through the crack sensor, determines the multi-dimensional force on the foot-end by analyzing the foot-end force model, realizes the real-time detection of the robot's ground contact force, and the detection result is accurate and reliable; Figure 1 Shown is a control block diagram of a robot foot-end multi-dimensional force detection method based on a crack sensor according to an embodiment of the present invention. The foot-end multi-dimensional force detection structure proposed in an embodiment of the present invention adds a pre-tightening screw to the base of the foot-end force sensor, which not only fixes the foot end, but also provides a convenient and quick calibration and zeroing method for the foot-end force sensor, and has an overload protection function; the size of the foot-end device is mainly based on the size of the base, and by changing the radius of the base, it can be adapted to robot calf structures of various structural forms, and the overall device can be quickly installed, with a reasonable structure, which improves the universality of the detection device. Figure 3 Shown is a structural diagram of a crack sensor of a foot-end device according to an embodiment of the present invention.

[0062] The embodiment of the present invention provides a robot foot end multi-dimensional force detection method based on a crack sensor. In order to prove the applicability of the present invention, it is applied to an example, which specifically includes the following steps:

[0063] S1: Install a crack sensor at the foot end of the robot to detect the external force;

[0064] Three crack sensors are installed on the foot of the robot, and the detection force range is 0 to 5000N. There are three crack strain sensors, arranged at intervals of 120°, around the foot, and the sensor slot on the base has an inclination of 45°. When the outer surface of the foot is subjected to force, the inner surface of the foot fits tightly with the crack sensor, so that the crack sensor is deformed by force, and the resistance value increases. The resistance change is then converted into an electrical signal of voltage output through the measurement circuit, thus completing the process of converting external force into an electrical signal. The sensing signals of the three crack sensors are U1, U2 and U3, and the three sensing signals are proportional to their respective forces F1, F2, and F3, as shown below:

[0065]

[0066] Wherein: F1, F2 and F3 are the external forces detected by the first, second and third crack sensors respectively; U1, U2 and U3 are the voltage output signals of the first, second and third crack sensors respectively; K represents the voltage-force conversion coefficient, which is 2 in the embodiment;

[0067] S2: Determine the force applied to the foot end according to the external force detected by the crack sensor;

[0068] Obtain the forces detected by the three crack sensors in step 1. The method for obtaining the forces acting on the foot end is as follows:

[0069]

[0070] Where: F t Indicates the force acting on the foot end; F x 、F y and F z Respectively represent the component forces in the directions of the x-axis, y-axis, and z-axis of the world coordinate system;

[0071] S3: Calculate the force direction of the foot end, determine whether the foot end is slipping, and adjust the robot gait;

[0072] S31: Calculate the angle between the force on the foot end and the horizontal ground to determine the force direction on the foot end;

[0073] When the force F t When acting on the surface of the foot end, a unique corresponding voltage is obtained, and the following set of equations is constructed to solve the force on the surface of the foot end;

[0074]

[0075] Then according to the magnitude of the three components, we can solve for F t The angle θ with the horizontal ground; according to F x and F y Solve for F t The angle ψ between the projection on the XY plane and the X-axis direction is as follows:

[0076]

[0077] Where: θ represents the angle between the foot force and the horizontal ground; ψ represents the angle between the foot force projected onto the horizontal ground and the X-axis direction;

[0078] S32: judging whether the foot end is slipping according to the force on the foot end and the angle between the force and the horizontal ground, and adjusting the gait of the robot;

[0079] According to the force on the foot end, the actual internal friction angle of the friction cone constraint is determined to further determine whether the foot end is slipping; the method for obtaining the internal friction angle is as follows:

[0080]

[0081] Where: θ z represents the internal friction angle of the friction cone constraint;

[0082] When the robot foot is in a swinging state, the reaction force F t is 0; then the vertical amplitude of the plantar reaction force is limited to the component force F in the direction of the z-axis of the world coordinate system z To ensure that there is no relative sliding between the sole of the foot and the ground, the horizontal component of the sole reaction force cannot be greater than the product of its vertical component and the sliding friction coefficient μ, that is, the friction cone condition is satisfied, as shown below:

[0083]

[0084] Where: μ represents the sliding friction coefficient;

[0085] Split the above equation into 4 linear constraints, and then combine them with the setting condition F z ≤5000N, a total of 5 linear constraints, the plantar reaction force constraints are integrated into a matrix, and the solution equations constructed by the ground friction coefficient μ are as follows:

[0086]

[0087] According to the ground sliding friction coefficient μ, the maximum internal friction angle of the friction cone can be calculated as follows;

[0088] θ max =arctanμ;

[0089] Where: θ max represents the maximum internal friction angle of the friction cone;

[0090] Then, according to the friction cone constraint calculated in step 32, the actual internal friction angle θ z Make a judgment; if the calculated friction cone constrains the actual internal friction angle θ z Smaller than the maximum internal friction angle θ of the friction cone max , the foot end does not slip; otherwise, the foot end slips. At this time, it is necessary to adjust the robot's gait and reduce the robot's stride to ensure the robot's stable motion state.

[0091] S4: Determine the multi-dimensional forces on the robot foot;

[0092] According to the force on the foot calculated in step 2 and the angle between the force on the foot and the horizontal ground calculated in step 3, the multi-dimensional force on the foot of the robot can be determined. Figure 2 The figure shows a simplified diagram of the force on the foot end of an embodiment of the present invention. Figure 7 The figure is a spatial schematic diagram of the force direction of the foot end according to an embodiment of the present invention. The exact direction of the force in space is determined by the angle θ between the force on the foot end and the horizontal ground and the angle ψ between the projection of the force on the foot end to the horizontal ground and the X-axis direction.

[0093] The second aspect of the present invention proposes a foot-end device of a robot foot-end multi-dimensional force detection method based on a crack sensor, characterized in that the foot-end device can directly detect the change of the foot-end multi-dimensional force and has an overload protection function, and the foot-end device includes a foot end 1, a baffle 2, a crack sensor 3, a base 4 and a pre-tightening bolt 5; Figure 3 Shown is a structural diagram of a crack sensor of a foot-end device according to an embodiment of the present invention;

[0094] The foot end 1 adopts a spherical design, and the spherical foot end 1 contacts the ground from all directions and has strong environmental adaptability.

[0095] The baffle 2 can better fix the foot end 1 and the three crack sensors 3, ensuring the tightness of the connection.

[0096] The crack sensor 3 is composed of a sensor base 9, a sensor body 7, a sensor cover 6 and a sensor slot 8; the crack sensor 3 is placed in the base 4 and connected to the sensor base 9; the base 4 and the sensor base 9 have high material rigidity, which limits the deformation of the crack strain sensor in other directions; the sensor body 7 is placed in the sensor slot 8 with a certain rigidity; the sensor cover 6 is attached to the upper and lower surfaces of the sensor slot 8; Figure 4 FIG. 1 is an axonometric diagram of a crack strain sensor according to an embodiment of the present invention; Figure 5 Shown is a front view of a crack strain sensor according to an embodiment of the present invention.

[0097] The base 4 is made of high-strength and high-rigidity materials, which serves the purpose of fixing parts and reducing deformation; at the same time, it has a simple structure and light weight, so as to achieve the purpose of reducing the difficulty of controlling the robot.

[0098] The pre-tightening bolt 5 is used to fix the foot end 1 and provides a convenient and quick calibration and zeroing method for the crack sensor 3; after the crack sensor 3 is installed on the robot leg, frequent removal and installation will accelerate the damage of the crack sensor 3, and zeroing and calibration are extremely inconvenient. In order to solve this problem, a pre-tightening screw is added to the base 4 of the foot end 1.

[0099] The crack sensor 3 specifically refers to a crack strain sensor. The main body of the crack strain sensor is an elastomer based on a scorpion crack sensor. The lower surface of the elastomer is provided with a plurality of parallel lyre-shaped cracks that can change when subjected to force. The change in their length affects the resistance value, thereby causing a voltage change in the crack strain sensor. The crack deformation size of the crack strain sensor is proportional to the voltage change.

[0100] The sensor base 9 is provided with an arc groove, which enables the crack strain sensor to deform and limits its deformation degree, preventing the crack strain sensor from deforming too much and causing failure, thereby causing failure of the force sensing of the foot end device and the upper control, and having an overload protection function. Figure 6 Shown is a force simulation diagram of the foot end of an embodiment of the present invention.

[0101] In summary, the robot foot multi-dimensional force detection method based on crack sensor and its structure proposed in this case have proven to have good results.

[0102] (1) The foot-end multi-dimensional force detection method proposed in the embodiment of the present invention converts the force change into the voltage signal change through the crack sensor, and determines the multi-dimensional force on the foot-end by analyzing the foot-end force model, thereby realizing the real-time detection of the robot's ground contact force, and the detection result is accurate and reliable;

[0103] (2) The foot-end multi-dimensional force detection device proposed in the embodiment of the present invention adds a pre-tightening screw to the base of the foot-end sensor, which not only fixes the foot end, but also provides a convenient and quick calibration and zeroing method for the foot-end force sensor, and has an overload protection function;

[0104] (3) The size of the foot-end device proposed in the embodiment of the present invention is mainly based on the size of the base. By changing the radius of the base, it can be adapted to robot calf structures of various structural forms. The accompanying drawings can prove that the overall structure of the device of this scheme is reasonable and can be installed quickly, thereby improving the universality of the detection device.

[0105] The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A robot foot end multi-dimensional force detection method based on crack sensor, characterized in that: It includes the following steps: Step 1: Install a crack sensor at the foot of the robot to detect the external force; The three crack sensors are installed at the foot ends of the robot respectively. The force changes on the outer surface of the foot ends are converted into voltage changes and output electrical signals through the crack sensors. The voltage output signals of the three crack sensors are U1, U2 and U3 respectively, and the three voltage output signals are proportional to their respective forces F1, F2 and F3, as shown below: Where: F1, F2 and F3 are the external forces detected by the first, second and third crack sensors respectively; U1, U2 and U3 are the voltage output signals of the first, second and third crack sensors respectively; K represents the voltage-force conversion coefficient; Step 2: Determine the force applied to the foot end according to the external force detected by the crack sensor; Obtain the forces detected by the three crack sensors in step 1. The method for obtaining the forces acting on the foot end is as follows: Where: F t Indicates the force acting on the foot end; F x 、F y and F z Respectively represent the component forces in the directions of the x-axis, y-axis, and z-axis of the world coordinate system; Step 3: Calculate the force direction of the foot end, determine whether the foot end is slipping, and adjust the robot gait; Step 31: Calculate the angle between the force on the foot end and the horizontal ground to determine the force direction on the foot end; When the force F t When acting on the surface of the foot end, a unique corresponding voltage is obtained, and the following set of equations is constructed to solve the force on the surface of the foot end; Then according to the magnitude of the three components, we can solve for F t The angle θ with the horizontal ground; according to F x and F y Solve for F t The angle ψ between the projection on the XY plane and the X-axis direction is as follows: Where: θ represents the angle between the foot force and the horizontal ground; ψ represents the angle between the foot force projected onto the horizontal ground and the X-axis direction; Step 32: According to the force on the foot end and the angle between the force and the horizontal ground, determine whether the foot end is slipping, and adjust the robot gait; According to the force on the foot end, the actual internal friction angle of the friction cone constraint is determined to further determine whether the foot end is slipping; the method for obtaining the internal friction angle is as follows: Where: θ z represents the internal friction angle of the friction cone constraint; Step 4: Determine the multi-dimensional forces acting on the robot foot; According to the force on the foot end calculated in step 2 and the angle between the force on the foot end and the horizontal ground calculated in step 3, the multi-dimensional force on the foot end of the robot can be determined.

2. The robot foot end multi-dimensional force detection method based on crack sensor according to claim 1 is characterized in that: In the step 1, three crack sensors are respectively installed on the foot ends of the robot. Specifically, the three crack strain sensors are arranged at intervals of 120°, surrounding the foot ends, and the inclination of the sensor slots on the base is 45°.

3. The robot foot end multi-dimensional force detection method based on crack sensor according to claim 1 is characterized in that: In step 1, the actual internal friction angle of the friction cone constraint is determined according to the force applied to the foot end, and whether the foot end is slipping is further determined, specifically: When the robot foot is in a swinging state, the reaction force F t is 0; then the vertical amplitude of the plantar reaction force is limited to the component force F in the z-axis direction of the world coordinate system z To ensure that there is no relative sliding between the sole of the foot and the ground, the horizontal component of the sole reaction force cannot be greater than the product of its vertical component and the sliding friction coefficient μ, satisfying the friction cone condition, as shown below: Where: μ represents the sliding friction coefficient; Split the above equation into 4 linear constraints, and then combine them with the setting condition F z ≤5000N, a total of 5 linear constraints, the plantar reaction force constraints are integrated into a matrix, and the solution equations constructed by the ground friction coefficient μ are as follows: According to the ground sliding friction coefficient μ, the maximum internal friction angle of the friction cone can be calculated as follows; θ max =arctanμ; Where: θ max represents the maximum internal friction angle of the friction cone; Then, according to the friction cone constraint calculated in step 32, the actual internal friction angle θ z Make a judgment; if the calculated friction cone constrains the actual internal friction angle θ z Less than the maximum internal friction angle θ of the friction cone max , the foot end does not slip; otherwise, the foot end slips. At this time, it is necessary to adjust the robot's gait and reduce the robot's stride to ensure the robot's stable motion state.

4. A foot-end device for implementing the robot foot-end multi-dimensional force detection method based on crack sensor according to any one of claims 1 to 3, characterized in that: It includes a foot end, a baffle, a crack sensor, a base and a pre-tightening bolt; The foot end is a spherical structure capable of contacting the ground from all directions; The baffle is capable of fixing the foot end and three crack sensors; The crack sensor comprises a sensor base, a sensor body, a sensor cover and a sensor slot; the crack sensor is placed in the base and connected to the sensor base; the sensor body is placed in the sensor slot with rigidity, and the sensor cover is attached to the upper and lower surfaces of the sensor slot; The pre-tightening bolt is used to fix the foot end and provide calibration and zeroing for the crack sensor. After the crack sensor is installed on the robot leg, the pre-tightening screw is added to the base of the foot end.

5. The foot-end device of the robot foot-end multi-dimensional force detection method based on crack sensor according to claim 4 is characterized in that: The crack sensor is a crack strain sensor. The main body of the crack strain sensor is an elastomer. The lower surface of the elastomer is provided with multiple groups of parallel lyre-shaped cracks that can change when subjected to force. The change in the length of the lyre-shaped cracks affects the resistance value, thereby causing the voltage of the crack strain sensor to change.

6. The foot-end device of the robot foot-end multi-dimensional force detection method based on crack sensor according to claim 4 is characterized in that: The sensor base is provided with an arc groove which enables the crack strain sensor to deform and limits the degree of deformation.

Images