An adaptive adjustable quasi-zero stiffness vibration isolation device suitable for variable load conditions

Abstract

This invention discloses an adaptive adjustable quasi-zero stiffness vibration isolation device suitable for variable load conditions, relating to the field of vibration isolation technology. The vibration isolation device includes an upper load-bearing platform, a lower support platform, a positive stiffness support mechanism, a negative stiffness adjustment mechanism, a drive adjustment mechanism, a guide mechanism, and a detection and control unit. The positive stiffness support mechanism includes a vertical spring. The negative stiffness adjustment mechanism includes a negative stiffness elastic element, a connecting rod assembly, a lateral push assembly, and a swing arm assembly. The negative stiffness elastic element undergoes elastic deformation under the drive of the connecting rod assembly and the lateral push assembly, outputting a nonlinear restoring force and providing damping effect that varies with deformation or loading speed during deformation. The nonlinear damping characteristics of the negative stiffness elastic element can provide energy dissipation in the resonance region, reducing the vibration response amplitude and improving the stability of the vibration isolation system. Compared with existing technologies, the device of this invention has excellent low-frequency vibration isolation performance and adaptive adjustment capability.

Description

Technical Field

[0001] This invention relates to the field of vibration control and vibration isolation technology, and in particular to an adaptive adjustable quasi-zero stiffness vibration isolation device suitable for variable load conditions. Background Technology

[0002] Vibration isolation devices are widely used in precision instruments, vehicle-mounted equipment, shipborne equipment, aerospace payload platforms, and electromechanical systems. Their main function is to reduce the transmission of external vibrations to the protected object and improve the stability and accuracy of equipment operation.

[0003] Traditional linear vibration isolation devices typically rely on elastic elements such as springs to provide support and vibration isolation. To achieve better low-frequency vibration isolation performance, it is usually necessary to reduce the system stiffness. However, reduced stiffness leads to increased static deformation and decreased load-bearing capacity, making it difficult to balance high static load-bearing capacity and low-frequency vibration isolation performance. To resolve this contradiction, quasi-zero stiffness vibration isolation technology has gradually gained attention. Quasi-zero stiffness vibration isolation devices typically couple positive stiffness mechanisms with negative stiffness mechanisms, enabling the system to have a low equivalent stiffness near the static equilibrium position, thereby achieving good low-frequency vibration isolation while maintaining high load-bearing capacity.

[0004] However, most existing quasi-zero stiffness vibration isolation devices are designed for fixed load conditions, and their structural parameters are usually difficult to adjust in real time or online according to load changes. When the external load changes, the static equilibrium position of the system will shift, causing the original quasi-zero stiffness working zone to deviate from the design position, resulting in a decrease in vibration isolation performance and even affecting system stability. In addition, some existing adjustable vibration isolation devices have problems such as complex adjustment structures, insufficient adjustment accuracy, or difficulties in engineering implementation, making it difficult to meet the comprehensive requirements for load-bearing capacity, low-frequency vibration isolation performance, and adaptability under variable load conditions.

[0005] Therefore, a vibration isolation device that can adjust the hinge position of the swing arm and the initial configuration of the negative stiffness mechanism according to load changes, thereby maintaining the quasi-zero stiffness characteristics of the system under different load conditions, has important engineering application value. Summary of the Invention

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An adaptive adjustable quasi-zero stiffness vibration isolation device suitable for variable load conditions includes an upper load-bearing platform, a lower support platform, a positive stiffness support mechanism, a negative stiffness adjustment mechanism, a drive adjustment mechanism, a guide mechanism, and a detection and control unit.

[0008] The positive stiffness support mechanism is disposed between the upper bearing platform and the lower support platform to support the load and provide vertical positive stiffness;

[0009] The negative stiffness adjustment mechanism is connected to the upper bearing platform. The negative stiffness adjustment mechanism includes a negative stiffness elastic element, a linkage assembly connected to the negative stiffness elastic element, a lateral push assembly and a hinged support. The negative stiffness elastic element undergoes elastic deformation under the drive of the linkage assembly and the lateral push assembly and outputs nonlinear restoring force and damping effect that varies with deformation or loading speed, thereby forming an equivalent negative stiffness.

[0010] The drive adjustment mechanism is connected to the negative stiffness adjustment mechanism and is used to change the hinge position of the swing arm assembly and change the initial configuration of the negative stiffness adjustment mechanism so that the vibration isolation device can adapt to different load conditions.

[0011] The guiding mechanism is used to constrain the upper support platform to move primarily vertically relative to the lower support platform.

[0012] The detection and control unit includes a force sensor and a controller. The force sensor is used to detect the load borne by the upper support platform, and the controller controls the drive adjustment mechanism to automatically adjust the hinge position of the swing arm assembly based on the detection signal.

[0013] Furthermore, the positive stiffness support mechanism includes multiple sets of vertical springs distributed circumferentially along the upper bearing platform, with each vertical spring disposed between the upper bearing platform and the lower support platform.

[0014] Furthermore, the negative stiffness adjustment mechanism includes multiple sets of negative stiffness units distributed circumferentially along the upper bearing platform, each negative stiffness unit including a negative stiffness elastic element, a connecting rod assembly, a lateral push assembly, and a hinged support.

[0015] Furthermore, the negative stiffness elastic element is preferably a silicone elastomer, which can provide not only nonlinear elastic restoring force during compression deformation, but also damping effect that varies with deformation or loading speed.

[0016] Furthermore, the drive adjustment mechanism includes a drive component, a lead screw transmission pair, a slide table, a movable slider, a support base, a transverse connecting shaft, a swing arm assembly, and a column plate. The movable slider is movably disposed on the slide table, the support base is disposed on the movable slider, and the transverse connecting shaft is disposed on the support base and rotatably connected to the swing arm assembly.

[0017] Furthermore, the movable slider moves along the slide table under the drive of the lead screw transmission pair to change the hinge position of the swing arm assembly.

[0018] Furthermore, the column plate can be moved vertically and cooperate with the relevant connecting parts in the negative stiffness adjustment mechanism to change the initial configuration of the negative stiffness adjustment mechanism.

[0019] Furthermore, the driving component is a motor, which is connected to the lead screw transmission pair to drive the movable slider to move along the slide table.

[0020] Furthermore, the guiding mechanism includes a guide rod and a linear bearing that cooperates with the guide rod to restrict the lateral displacement and rotational degrees of freedom of the upper bearing platform.

[0021] Furthermore, the vibration isolation device also includes a detection and control unit, which includes a force sensor and a controller. The force sensor is used to detect the load or its changes on the upper bearing platform. The controller controls the drive adjustment mechanism to operate according to the load signal, thereby automatically changing the hinge position of the swing arm assembly and the initial configuration of the negative stiffness adjustment mechanism, so that the vibration isolation device can maintain quasi-zero stiffness characteristics under different load conditions.

[0022] Furthermore, the controller has a pre-stored mapping relationship between the load signal and the adjustment amount of the drive adjustment mechanism. The mapping relationship is used to determine the displacement of the moving slider or the hinge position of the swing arm assembly based on the detected load, so that the horizontal push assembly is at or close to the horizontal static balance position under the corresponding load.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] By employing silicone elastic elements with nonlinear damping characteristics, an energy dissipation mechanism is introduced while achieving negative stiffness characteristics. This enables the vibration isolation device to effectively suppress vibration response peaks in the resonance region and provide higher damping when the load changes abruptly or the vibration amplitude is large, thereby improving the system's operational stability and dynamic response performance.

[0025] By establishing a mapping relationship between the load signal and the adjustment amount of the drive adjustment mechanism in the controller, the drive adjustment mechanism can automatically determine the hinge position adjustment amount of the swing arm assembly according to the load borne by the upper bearing platform, so that the lateral push assembly can be quickly adjusted to or close to the horizontal static balance position under different load conditions.

[0026] By setting a drive adjustment mechanism, the hinge position of the swing arm assembly can be changed and the initial configuration of the negative stiffness adjustment mechanism can be altered, thereby adapting to different load conditions and compensating for the static balance point offset caused by load changes.

[0027] Position adjustment is achieved through a lead screw drive pair, slide table, and moving slider, resulting in high adjustment accuracy, a clear structure, and ease of engineering implementation.

[0028] By adjusting the vertical column plate, the initial geometric relationship of the relevant components of the negative stiffness adjustment mechanism can be further changed, giving the system strong adjustability and adaptability.

[0029] The above method achieves automatic matching between the negative stiffness adjustment mechanism and the positive stiffness support mechanism, enabling the system to maintain quasi-zero stiffness characteristics under different load conditions. This avoids the problem of repeated manual adjustment required in traditional devices and improves the self-adaptive capability and adjustment efficiency of the vibration isolation device. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings are briefly described below:

[0031] Figure 1 This is a perspective view of the external structure of the present invention;

[0032] Figure 2 This is a side view of the external structure of the present invention;

[0033] Figure 3 This is a diagram of the negative stiffness structure of the present invention;

[0034] Figure 4 This is a diagram of the drive adjustment mechanism of the present invention;

[0035] Figure 5 This is a diagram of the guiding mechanism of the present invention;

[0036] The components include: 1. Upper bearing platform; 2. Upper base; 3. Reinforcing plate; 4. Side reinforcing plate; 5. Guide rod; 6. Column plate; 7. Spring mounting seat; 8. Vertical spring; 9. Lower support platform; 10. Horizontal clamping plate; 11. Column rod; 12. Negative stiffness elastic element; 13. Linkage assembly; 14. Horizontal push assembly; 15. Hinge support; 16. Drive component; 17. Screw transmission pair; 18. Slide table; 19. Moving slider; 20. Support seat; 21. Horizontal connecting shaft; 22. Linear bearing; 23. Swing arm assembly. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the accompanying drawings and working principle. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0038] This embodiment provides an adjustable quasi-zero stiffness vibration isolation device suitable for variable load conditions, including an upper bearing platform, a lower support platform, a positive stiffness support mechanism, a negative stiffness adjustment mechanism, a drive adjustment mechanism, a guide mechanism, and a detection and control unit.

[0039] The upper load-bearing platform is located at the top of the device and is used to support external equipment or test loads. The lower support platform is located at the bottom of the device and is used to install and support various functional mechanisms. The upper load-bearing platform and the lower support platform are connected by a positive stiffness support mechanism, a negative stiffness adjustment mechanism, and a guide mechanism.

[0040] 1. Positive stiffness support mechanism

[0041] In this embodiment, the positive stiffness support mechanism includes multiple sets of vertical springs distributed circumferentially along the upper bearing platform. Each vertical spring is respectively disposed between the upper bearing platform and the lower support platform to jointly support the upper bearing platform and its load, and to provide vertical positive stiffness. The vertical springs can also be other elastic elements capable of providing vertical elastic support.

[0042] The positive stiffness support mechanism is used to bear the main static load of the system and to provide vertical restoring force when the upper bearing platform undergoes vertical displacement.

[0043] 2. Negative stiffness adjustment mechanism

[0044] The negative stiffness adjustment mechanism is disposed between the upper bearing platform and the lower support platform, and is connected to the upper bearing platform. In this embodiment, the negative stiffness adjustment mechanism includes multiple sets of negative stiffness units distributed circumferentially. Each negative stiffness unit includes a negative stiffness elastic element, a connecting rod assembly, a lateral push assembly, and a hinged support.

[0045] The elastic element can be made of silicone. The connecting rod assembly is connected to the negative stiffness elastic element, and the lateral push assembly is rotatably connected to the upper connection point and the lower hinge position, respectively. The hinge support is used to provide a hinged mounting base for related components.

[0046] When the upper support platform undergoes vertical displacement, the lateral push assembly drives the linkage assembly to move, causing the negative stiffness elastic element to undergo elastic deformation and output a nonlinear restoring force. This nonlinear restoring force, together with the positive stiffness provided by the positive stiffness support mechanism, enables the vibration isolation device to form a low equivalent stiffness near the static equilibrium position, thereby achieving quasi-zero stiffness characteristics.

[0047] 3. Guiding mechanism

[0048] The guiding mechanism is used to constrain the upper support platform's movement relative to the lower support platform primarily along the vertical direction. In this embodiment, the guiding mechanism includes a guide rod and a linear bearing that cooperates with the guide rod. The guide rod is arranged vertically, and the linear bearing is installed at the relevant connection point to limit the lateral displacement and rotational degrees of freedom of the upper support platform, thereby improving the stability of the upper support platform's vertical movement.

[0049] 4. Drive adjustment mechanism

[0050] The drive adjustment mechanism is mounted on the lower support platform and connected to related mechanisms. It is used to change the hinge position of the swing arm assembly and the initial configuration of the negative stiffness adjustment mechanism. In this embodiment, the drive adjustment mechanism includes a drive component, a lead screw transmission pair, a slide table, a movable slider, a support base, a transverse connecting shaft, a swing arm assembly, and a column plate.

[0051] 5. Detection and control unit

[0052] The detection and control unit includes a force sensor and a controller. The force sensor is used to detect the load or its changes on the upper bearing platform. The controller controls the drive adjustment mechanism to operate according to the load signal, thereby automatically changing the hinge position of the swing arm assembly and the initial configuration of the negative stiffness adjustment mechanism, so that the vibration isolation device can maintain quasi-zero stiffness characteristics under different load conditions.

[0053] Working principle: In this embodiment, the horizontal push assembly 14 is taken as the design static equilibrium position of the vibration isolation device when it is in a horizontal position. In this state, the positive stiffness support mechanism and the negative stiffness adjustment mechanism achieve stiffness matching, so that the system has quasi-zero stiffness characteristics near the static equilibrium position.

[0054] When an external load is applied to the upper bearing platform 1, the upper bearing platform 1 moves downward relative to the lower support platform 9 along the guide mechanism under the load. The guide rod 5 in the guide mechanism cooperates with the linear bearing 22 to constrain the upper bearing platform 1 to move mainly vertically and limit its lateral displacement and rotational degrees of freedom, thereby ensuring the stability of the vibration isolation device during its movement.

[0055] As the upper bearing platform 1 moves downward, the transverse connecting piece 10 and the column plate 6 move upward under the action of the mechanism, compressing the vertical spring 8. The vertical spring 8 extends and retracts along the axial direction of the column rod 11, which guides and laterally limits the vertical spring 8 to prevent it from shifting laterally or becoming unstable during compression. The compressed vertical spring 8 generates an elastic restoring force that pulls its two ends away from each other. This elastic restoring force is transmitted through the relevant connecting structure and participates in supporting the external load, thus enabling the positive stiffness support mechanism to exhibit vertical positive stiffness characteristics.

[0056] Simultaneously, the vertical displacement of the upper bearing platform 1 is transmitted to the negative stiffness adjustment mechanism through the relevant connecting structure. The lateral push assembly 14 rotates under hinge action, driving the connecting rod assembly 13 to move in an approximately horizontal direction. The movement of the connecting rod assembly 13 causes the negative stiffness elastic element 12 to undergo compressive deformation. The negative stiffness elastic element 12 is preferably a silicone elastomer or other materials with nonlinear elastic properties. When the negative stiffness elastic element 12 undergoes compressive deformation, it outputs a nonlinear restoring force related to the amount of deformation. Furthermore, the negative stiffness elastic element 12 is preferably a silicone elastomer. Silicone materials not only exhibit nonlinear mechanical properties during compression but also have significant viscoelastic characteristics; their damping increases with the increase of deformation amplitude or loading speed.

[0057] During the operation of the vibration isolation device, when the system vibration amplitude is large or close to the resonance region, the silicone elastic element can provide significant damping energy dissipation, thereby effectively reducing the system vibration response amplitude and suppressing the resonance peak. When the external load changes abruptly, the damping effect can quickly dissipate the impact energy, reduce the system's excessive vibration, and improve the dynamic stability of the vibration isolation device. This restoring force is transmitted through the connecting rod assembly 13, the lateral push assembly 14, and the swing arm assembly 23 and converted into a vertical equivalent force.

[0058] Because the negative stiffness adjustment mechanism is symmetrically arranged on both sides, the horizontal component of the force generated by the negative stiffness elastic element 12 cancels each other out on both sides, while the vertical component formed after being converted by the mechanism participates in balancing the load on the upper bearing platform 1. Through this nonlinear force transmission relationship, the negative stiffness adjustment mechanism forms an equivalent negative stiffness characteristic in the vertical direction.

[0059] Near the design static balance point where the horizontal push assembly 14 is in a horizontal position, the equivalent negative stiffness output by the negative stiffness adjustment mechanism cancels out the positive stiffness provided by the vertical spring 8, making the total equivalent stiffness of the system close to zero, thereby achieving quasi-zero stiffness characteristics and improving the low-frequency vibration isolation performance of the vibration isolation device.

[0060] When the external load changes, the original static balance position will shift, and the transverse push assembly 14 will deviate from its horizontal design position, causing the stiffness matching relationship between the positive stiffness support mechanism and the negative stiffness adjustment mechanism to change, thereby affecting the vibration isolation performance.

[0061] To achieve adaptive adjustment under varying load conditions, this embodiment incorporates a detection and control unit within the vibration isolation device. The detection and control unit includes a force sensor mounted on the upper support platform 1 or its connecting portion, and a controller electrically connected to the force sensor. The force sensor is used to detect the load or load change signal borne by the upper support platform 1 in real time and transmit the detection signal to the controller.

[0062] The controller calculates the required adjustment amount based on the load signal and the preset control strategy, and outputs a control signal to the drive unit 16. The drive unit 16 drives the lead screw transmission pair 17 to move, causing the movable slider 19 to move along the slide table 18. Since the support base 20 is mounted on the movable slider 19, and the transverse connecting shaft 21 is mounted on the support base 20 and rotatably connected to the swing arm assembly 23, the displacement of the movable slider 19 can cause a change in the hinge position of the swing arm assembly 23.

[0063] When the hinge position of the swing arm assembly 23 changes, the initial angle of the swing arm assembly 23, the rotation relationship of the transverse push assembly 14, and the initial position of the connecting rod assembly 13 change accordingly, thereby changing the compression state of the negative stiffness elastic element 12 and its nonlinear force output characteristics, and thus adjusting the equivalent negative stiffness of the negative stiffness adjustment mechanism in the vertical direction.

[0064] Through the aforementioned automatic adjustment process, the transverse thrust assembly 14 can return to or approach its designed horizontal static equilibrium position under different load conditions. This allows the positive stiffness support mechanism and the negative stiffness adjustment mechanism to re-achieve stiffness matching near the new equilibrium position, enabling the system to maintain near-zero stiffness characteristics under different load conditions. The adjustment process is based on the mapping relationship between the load signal and the drive adjustment amount, allowing the system to quickly adjust to the corresponding equilibrium state under different load conditions.

[0065] In summary, this invention, by setting up a detection and control unit and combining load detection with a drive adjustment mechanism, realizes the automatic adjustment function of the vibration isolation device under variable load conditions. Compared with traditional quasi-zero stiffness vibration isolation devices that require manual adjustment, this invention can automatically adjust the hinge position of the swing arm assembly and the initial configuration of the negative stiffness adjustment mechanism according to load changes, so that the lateral push assembly is always at or close to the horizontal design static balance position, thereby significantly improving the adaptability and ease of use of the vibration isolation device.

[0066] It should be noted that, without departing from the concept of this invention, the above structure can be replaced or changed as follows:

[0067] In addition to a motor, the driving component can also be an electric cylinder, a servo actuator, or other driving device capable of providing adjustable displacement; the cooperation between the slide table and the moving slider can be a linear guide pair, a slide block pair, or other guide pairs; the number and circumferential distribution of the vertical springs in the positive stiffness support mechanism can be adjusted according to the load-bearing requirements; the negative stiffness elastic element is preferably a silicone elastomer, but other elastic elements capable of producing nonlinear elastic deformation can also be used.

[0068] Those skilled in the art will understand that the above embodiments are merely preferred embodiments of the present invention, and all equivalent substitutions, improvements or modifications made in accordance with the present invention specification and claims should be included within the protection scope of the present invention.

Claims

1. An adaptive adjustable quasi-zero stiffness vibration isolation device suitable for variable load conditions, characterized in that, include: Upper carrier platform (1); Lower support platform (9); The positive stiffness support mechanism disposed between the upper bearing platform (1) and the lower support platform (9) includes a vertical spring (8) for providing vertical positive stiffness support; The negative stiffness adjustment mechanism connected to the upper bearing platform (1) includes a negative stiffness elastic element (12), a linkage assembly (13) connected to the negative stiffness elastic element (12), a transverse push assembly (14) connected to the linkage assembly (13), and a swing arm assembly (23) rotatably connected to the transverse push assembly (14); the negative stiffness elastic element (12) undergoes elastic deformation and outputs nonlinear restoring force under the drive of the linkage assembly (13) and the transverse push assembly (14), forming an equivalent negative stiffness; The drive adjustment mechanism includes a drive component (16), a lead screw transmission pair (17) connected to the drive component (16), a movable slider (19) cooperating with the lead screw transmission pair (17), a slide table (18) for supporting the movable slider (19), a support seat (20) disposed on the movable slider (19), a transverse connecting shaft (21) disposed on the support seat (20), and a column plate (6); the transverse connecting shaft (21) is rotatably connected to the swing arm assembly (23), and when the movable slider (19) moves along the slide table (18), it can change the hinge position of the swing arm assembly (23) and adjust the initial configuration of the negative stiffness adjustment mechanism; A guiding mechanism is provided between the upper bearing platform (1) and the lower support platform (9) to constrain the upper bearing platform (1) to move mainly vertically relative to the lower support platform (9); The detection control unit includes a force sensor disposed on the upper support platform (1) or its connection portion and a controller electrically connected to the force sensor, the controller being electrically connected to the drive unit (16); The controller controls the drive (16) to drive the movable slider (19) to move along the slide (18) according to the load signal detected by the force sensor, so as to automatically adjust the hinge position of the swing arm assembly (23), so that the horizontal push assembly (14) is in or close to the horizontal static balance position under different load conditions, and so that the positive stiffness support mechanism and the negative stiffness adjustment mechanism form a quasi-zero stiffness characteristic near the balance position.

2. The adaptive adjustable quasi-zero stiffness vibration isolation device according to claim 1, characterized in that: The vertical spring (8) extends and retracts along the axial direction of the column rod (11), and the column rod (11) is used to guide and laterally limit the vertical spring (8).

3. The adaptive adjustable quasi-zero stiffness vibration isolation device according to claim 1, characterized in that: The negative stiffness adjustment mechanism includes multiple sets of negative stiffness units distributed circumferentially along the upper bearing platform (1). Each negative stiffness unit includes the negative stiffness elastic element (12), the connecting rod assembly (13), the transverse push assembly (14), and the hinge support (15).

4. The adaptive adjustable quasi-zero stiffness vibration isolation device according to claim 1, characterized in that: The movable slider (19) moves along the slide (18) under the drive of the lead screw transmission pair (17) to change the hinge position of the swing arm assembly (23).

5. The adaptive adjustable quasi-zero stiffness vibration isolation device according to claim 1, characterized in that: The column plate (6) can be moved vertically and cooperates with the relevant connecting parts in the negative stiffness adjustment mechanism to change the initial configuration of the negative stiffness adjustment mechanism.

6. The adaptive adjustable quasi-zero stiffness vibration isolation device according to claim 1, characterized in that: The driving component (16) is a motor, and the motor is connected to the lead screw transmission pair (17) for transmission.

7. The adaptive adjustable quasi-zero stiffness vibration isolation device according to claim 1, characterized in that: The guiding mechanism includes a guide rod (5) and a linear bearing (22) that cooperates with the guide rod (5) to limit the lateral displacement and rotational freedom of the upper bearing platform (1).

8. The adaptive adjustable quasi-zero stiffness vibration isolation device according to claim 1, characterized in that: The lower part of the swing arm assembly (23) is rotatably connected to the support base (20) via the transverse connecting shaft (21), and the upper part of the swing arm assembly (23) is rotatably connected to the upper bearing platform (1) or its connecting parts.

9. The adaptive adjustable quasi-zero stiffness vibration isolation device according to claim 1, characterized in that: The negative stiffness elastic element (12) is a silicone elastomer, which provides both nonlinear restoring force and damping effect that varies with deformation or loading speed during the compression deformation process.

10. The adaptive adjustable quasi-zero stiffness vibration isolation device according to claim 1, characterized in that: The controller has a pre-stored mapping relationship between load signal and adjustment amount of drive adjustment mechanism. The mapping relationship is used to determine the displacement of the moving slider (19) or the hinge position adjustment amount of the swing arm assembly (23) based on the load signal detected by the force sensor.

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