Rigidity-adjustable reconfigurable nonlinear rotation series elastic driver

Abstract

The invention discloses a reconfigurable nonlinear rotation series elastic driver with adjustable rigidity. The driver includes an input member, an adjustable stiffness flexible member, an output member, and a support member. The input part comprises a collimation direct drive motor, a motor fixing device and an input ring and is used for being connected with an external driving force so as to transmit the external driving torque to the rigidity-adjustable flexible part. The rigidity-adjustable flexible part comprises an axial space spring array composed of linear extension springs and used for endowing the driver with the nonlinear characteristic. And the output component comprises an output ring with an adjustable anchor point and a driver output connecting rod, and is used for realizing an auxiliary training task in human-computer interaction. According to the axial space spring array, the driver can be endowed with the adjustable rigidity characteristic without replacing hardware through adjustable anchor points designed through geometric parameters. The supporting component comprises a driver support used for supporting the rigidity-adjustable reconfigurable nonlinear rotation series elastic driver.

Description

Technical Field

[0001] The invention relates to the technical field of robots, and in particular to a reconfigurable nonlinear rotating series elastic driver with adjustable stiffness. Background Art

[0002] In recent years, assistive robots for stroke rehabilitation and capacity enhancement have developed rapidly, especially gait-assisted exoskeletons, which have performed outstandingly in improving users' motor functions and quality of life. In such applications, assistive robots must interact directly with humans physically. In order to improve the safety of physical human-machine interaction, driver design is crucial. Compliance is the core performance indicator of assistive robots, which is of great significance for improving dynamic adaptability, environmental robustness and achieving safe interaction. Compared with rigid drive systems, flexible drives are superior in impact force absorption and external load perception. The series elastic drive is the most representative flexible drive structure. By introducing elastic elements between the rigid drive and the load, low output impedance, good reverse drivability, impact resistance and efficient and stable force transmission are achieved, which significantly improves the safety of physical human-machine interaction.

[0003] Under the premise of ensuring the safety of human-computer interaction, the design of series elastic actuators faces multiple requirements and challenges. First, it is necessary to have an inherent force sensing ability to achieve accurate measurement and adjustment of the interaction force, which relies on clear and predictable torque-deformation characteristics. Secondly, human-computer interaction scenarios usually require the actuator to have low friction, small hysteresis, no dead zone and bidirectional consistent force output to adapt to the control requirements of fast direction switching. In addition, good compliance is also the key to ensure comfortable and safe interaction, requiring the actuator to have low stiffness and large deformation capacity. However, series elastic actuators usually use springs with fixed stiffness as elastic elements for force transmission, resulting in fundamental limitations of the actuator. On the one hand, soft springs can produce high force control fidelity and low output impedance, but at the same time limit the force output range and bandwidth. On the other hand, hard springs increase the force bandwidth but reduce the interaction compliance. Summary of the invention

[0004] In view of the above problems, a reconfigurable nonlinear rotational series elastic actuator with adjustable stiffness is provided, aiming to effectively solve the inherent limitations of the above series elastic actuator.

[0005] The purpose of the present invention is to propose a reconfigurable nonlinear rotary series elastic actuator with adjustable stiffness. The reconfigurable nonlinear rotary series elastic actuator has excellent mechanical properties, such as good compliance, low friction, small hysteresis, and sufficient force bandwidth and output force. The reconfigurable nonlinear rotary series elastic actuator has advantages in stiffness range, output torque, compactness, and light weight. At the same time, a compliant drive unit with compactness, light weight and high-precision force control capability is provided for a wearable exoskeleton robot. The problem to be solved by the present invention is achieved by the following technical solutions: A reconfigurable nonlinear rotary series elastic actuator with adjustable stiffness includes: an input component, the input component includes a quasi-direct drive motor, a motor fixing device, and an input ring, which is used to connect with an external driving force to transmit the external driving torque to an adjustable stiffness flexible component. An adjustable stiffness flexible component, the adjustable stiffness flexible component includes an axial space spring array composed of linear tension springs, which is used to give the driver nonlinear and adjustable stiffness characteristics. An output component, the output component includes an output ring and a driver output connecting rod, which is used to realize auxiliary training tasks in human-computer interaction. A support component includes a driver bracket for supporting the reconfigurable nonlinear rotation series elastic driver.

[0006] The quasi-direct drive motor integrates a 9:1 planetary reducer, a single-turn absolute encoder and a highly integrated driver, achieving smooth operation with large torque and facilitating the compact design of the reconfigurable nonlinear rotary series elastic driver. The quasi-direct drive motor is fastened to the motor fixing device by a hexagon socket screw. The output end of the quasi-direct drive motor is fixed to the rear end of the input ring by a hexagon socket screw. The quasi-direct drive motor drives the input ring to move and causes the linear tension spring to deform. The thin-walled bearing is installed between the output ring and the driver housing to reduce friction. The rotary encoder consists of a reading head and a permanent magnet ring. The permanent magnet ring is fixed to the output ring, and the reading head is fixed to the driver housing for real-time reading of the rotation angle of the output ring. The quasi-direct drive motor has a single-turn absolute encoder and the rotary encoder to measure the deflection angle of the axial space spring array by difference, and accurately calculate the output torque of the reconfigurable nonlinear rotary series elastic driver.

[0007] The axial space spring array is the core structure of the reconfigurable nonlinear rotation series elastic actuator. The input ring and the output ring are coaxially configured and coupled by a linear tension spring. The flange deep groove ball bearing is used to achieve relative rotation and reduce friction. The input ring and the output ring include an inner ring and an outer ring, respectively. The inner and outer rings are each configured with four groups of symmetrically distributed linear tension springs, and the phase angle between adjacent groups is 90°. When the input ring and the output ring undergo relative angular displacement, the linear tension spring always maintains a pre-tensioned state, and its tangential component force forms a synthetic torque in the rotation plane.

[0008] The purpose of designing the four groups of linear tension springs in the inner ring of the axial space spring array is to increase the output torque of the reconfigurable nonlinear rotation series elastic actuator and optimize the compactness of the structure. The four groups of springs in the outer ring of the axial space spring array are reconstructed into three different configurations by changing the initial deflection angle. The output ring includes an adjustable anchor point. Based on the design of the adjustable anchor point based on geometric parameters, the axial space spring array can achieve rapid switching of stiffness modes without hardware reconstruction. Through the multi-modal stiffness characteristics from nonlinear to quasi-linear, it covers the full working conditions from compliant interaction to high dynamic loads, significantly improving the task adaptability of the reconfigurable nonlinear rotation series elastic actuator in auxiliary robot scenarios such as rehabilitation training, gait correction and weight-bearing exoskeletons.

[0009] Compared with the prior art, the present invention has achieved the following technical effects: 1. The axial space spring array can give the reconfigurable nonlinear rotation series elastic actuator adjustable stiffness characteristics through adjustable anchor points designed based on geometric parameters without replacing hardware. 2. A flange deep groove ball bearing is installed between the input ring and the output ring to reduce the friction during the rotation of the axial space spring array. 3. The inner and outer rings of the input ring and the output ring are both installed with linear tension springs, which effectively improves the compactness and output torque of the reconfigurable nonlinear rotation series elastic actuator. 4. By adjusting the initial deflection angle of the axial space spring array, a high nonlinear to quasi-linear stiffness curve is achieved, thereby achieving task-oriented stiffness optimization. High nonlinear stiffness is suitable for applications such as assistance that require high low impedance and precise interactive force control; medium-low nonlinearity or low nonlinear stiffness is suitable for scenes such as gait correction and weight-bearing exoskeletons that require stable high-bandwidth output. 5. The single-turn absolute encoder of the quasi-direct drive motor and the rotary encoder are used to obtain the rotation angle of the axial space spring array by difference, and the output torque of the reconfigurable nonlinear rotary series elastic actuator is accurately calculated through the equivalent stiffness model. 6. The reconfigurable nonlinear rotary series elastic actuator achieves a balanced design between safety interaction, dynamic load adaptability and system integration through the coordinated optimization of stiffness, torque and mass, providing a highly compliant, strong drive and low inertia drive device for assistive robots. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is an external view of the reconfigurable nonlinear rotation series elastic actuator according to the present invention; Figure 2 This is an internal view of the reconfigurable nonlinear rotation series elastic actuator according to the present invention; Figure 3 This is an exploded view of the reconfigurable nonlinear rotation series elastic actuator according to the present invention; Figure 4 This is an exploded view of the axial space spring array of the present invention; Figure 5 This is a distribution diagram of the linear tension spring of the present invention; Figure 6 This is a schematic diagram of the axial space spring array configuration 1 of the present invention; Figure 7 This is a schematic diagram of the axial space spring array configuration 2 of the present invention; Figure 8 It is a schematic diagram of the axial space spring array configuration 3 described in the present invention.

[0011] In the figure, there are a quasi-direct drive motor 1, a motor fixture 2, an input ring 3, a linear tension spring 4, an adjustable anchor point 5, an output ring 6, a thin-walled bearing 7, a rotary encoder 8, a reading head 8.1, a permanent magnet ring 8.2, a drive housing 9, a drive bracket 10, a drive output connecting rod 11, and a flange deep groove ball bearing 12. DETAILED DESCRIPTION

[0012] The following is combined with Figure 1-8 The present invention is further described: The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. The described embodiments are part of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0013] In the description of the present invention, it should be noted that the directions or positional relationships indicated by terms such as “center”, “up”, “down”, “left”, “right”, “vertical”, “horizontal”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. Therefore, they cannot be understood as limitations on the present invention.

[0014] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example: it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0015] like Figure 1 , Figure 2 and Figure 3 As shown, the first embodiment of the present invention provides a reconfigurable nonlinear rotation series elastic driver with adjustable stiffness based on the prior art, including: an input component, the input component includes a quasi-direct drive motor, a motor fixing device, and an input ring, which is used to connect with an external driving force to transmit the external driving torque to an adjustable stiffness flexible component. An adjustable stiffness flexible component, the adjustable stiffness flexible component includes an axial space spring array composed of linear tension springs, which is used to give the driver nonlinear and adjustable stiffness characteristics. An output component, the output component includes an output ring with an adjustable anchor point and a driver output connecting rod, which is used to realize auxiliary training tasks in human-computer interaction. A support component, the support component includes a driver bracket, which is used to support the reconfigurable nonlinear rotation series elastic driver.

[0016] Figure 1 FIG. 1 is an external view of the reconfigurable nonlinear rotation series elastic actuator. Figure 1 As shown, the reconfigurable nonlinear rotation series elastic actuator is fastened to the actuator fixing bracket by a hexagon socket screw. A connecting rod is installed at the end of the output ring to realize the auxiliary training task in human-computer interaction.

[0017] Figure 2 FIG. 1 is an internal view of the reconfigurable nonlinear rotation series elastic actuator. Figure 2 As shown in the figure, the reconfigurable nonlinear rotation series elastic actuator has a compact structure and a lightweight design, which is convenient for integrated application. The lightweight design of the reconfigurable nonlinear rotation series elastic actuator helps the auxiliary robot improve its movement flexibility and reduce the burden of the mechanical structure. At the same time, through the coordinated optimization of stiffness, torque and mass, a balanced design is achieved between safe interaction, dynamic load adaptability and system integration.

[0018] Figure 3 Exploded view of a reconfigurable nonlinear rotational series elastic actuator with adjustable stiffness. Figure 3As shown, the quasi-direct drive motor is fastened to the motor fixing device by using a hexagon socket screw. The output end of the quasi-direct drive motor is fastened to the rear end of the input ring by using a hexagon socket screw. One end of the linear tension spring is connected to the input ring, and the other end is connected to the output ring. The end of the output ring is the output end of the reconfigurable nonlinear rotation series elastic driver. The rotary encoder is composed of a reading head and a permanent magnet ring. The reading head is fastened to the driver housing by using a flat head screw. The permanent magnet ring is fastened to the output ring by using a flat head screw. The rotary encoder is used to measure the output angle of the reconfigurable nonlinear rotation series elastic driver. The quasi-direct drive motor has a single-turn absolute encoder for obtaining the angle of the motor shaft. The quasi-direct drive motor has a single-turn absolute encoder and the rotary encoder, and the deformation of the axial space spring array composed of linear tension springs can be calculated by subtracting the single-turn absolute encoder and the rotary encoder. The driver housing is fastened to the motor fixing device by using a hexagon socket screw. The motor fixing device is designed with a positioning boss to improve the assembly accuracy and structural stability when connected to the driver housing.

[0019] like Figure 4 This is an exploded view of an axial space spring array. Figure 4 The axial space spring array shown is composed of an input ring, a linear tension spring, a flange deep groove ball bearing, and an output ring. The stepped shaft at the front end of the input ring is transitionally matched with the inner ring of the flange deep groove ball bearing, and the outer ring of the flange deep groove ball bearing is installed inside the output ring with an interference fit. The upper and lower ends of the linear tension spring are respectively connected to the input ring and the output ring to form an axial space spring array to achieve structural flexible coupling. The input ring and the output ring are both composed of an inner ring and an outer ring, and linear tension springs are installed on their inner and outer rings. Adjustable anchor points are evenly distributed on the output ring. The output ring is designed with adjustable anchor points based on geometric parameter design, which is used to change the initial deflection angle of the linear tension spring, and the reconfigurable nonlinear rotation series elastic actuator is endowed with adjustable stiffness characteristics without replacing the linear tension spring.

[0020] like Figure 5 is a distribution diagram of a linear tension spring. Figure 5 As shown, the input ring and the output ring include an inner ring and an outer ring, respectively. The inner ring and the outer ring are each configured with four pairs of symmetrically distributed linear tension springs, and the phase angle between adjacent groups is 90°. The purpose of installing the linear tension springs on the inner rings of the input ring and the output ring is to enhance the output torque of the driver and improve the compactness of the structure. The purpose of installing the linear tension springs on the outer rings of the input ring and the output ring is to change the initial deflection angle of the linear tension spring through the adjustable anchor point, so that the reconfigurable nonlinear rotation series elastic driver can achieve nonlinear and adjustable stiffness characteristics.

[0021] like Figure 6-Figure 8is the axial space spring array of the linear tension spring at different initial deflection angles. Figure 6-Figure 8 As shown in the figure, as the initial deflection angle of the linear tension spring increases, the output stiffness of the reconfigurable nonlinear rotary series elastic actuator tends to increase. When the initial deflection angle of the linear tension spring is zero, the system exhibits highly nonlinear stiffness characteristics, which is suitable for health assistance tasks with high requirements for low impedance and high-precision force control. As the initial deflection angle of the linear tension spring increases, the output stiffness tends to be moderately nonlinear or low nonlinear, which is beneficial to improving the stability and bandwidth of the torque output, and is suitable for scenarios such as gait correction and load assistance.

[0022] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solutions formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept.

Claims

1. A reconfigurable nonlinear rotary series elastic actuator with adjustable stiffness, characterized in that: include: An input component, the input component comprising a quasi-direct drive motor (1), a motor fixture (2), and an input ring (3), which is used to connect with an external driving force to transmit the external driving torque to the adjustable stiffness flexible component; the quasi-direct drive motor (1) is firmly installed through the motor fixture (2), and its output end is connected to the input ring (3) to drive the adjustable stiffness flexible component to move; the adjustable stiffness flexible component, the adjustable stiffness flexible component comprising an axial space spring array composed of linear tension springs (4), which is used to give the reconfigurable nonlinear rotational series elastic actuator nonlinear and adjustable stiffness characteristics; the inner ring of the axial space spring array Four groups of linear tension springs increase the output torque of the reconfigurable nonlinear rotational series elastic actuator and optimize the compactness of the structure; the four groups of springs in the outer ring of the axial space spring array are reconfigured into three different configurations by changing the initial deflection angle; when the initial deflection angle of the linear tension spring (4) is zero, the system exhibits highly nonlinear stiffness characteristics, which is suitable for auxiliary tasks with high requirements for low impedance and high-precision force control; as the initial deflection angle of the linear tension spring (4) increases, the output stiffness tends to medium nonlinearity or low nonlinearity, which is conducive to improving the stability and bandwidth of the torque output, and is suitable for scenes such as gait correction and load assistance; An output component, the output component comprising an output ring (6) with an adjustable anchor point (5) and a driver output connecting rod (11), used to implement auxiliary training tasks in human-computer interaction; and a support component, the support component comprising a driver bracket (10), used to support the reconfigurable nonlinear rotational series elastic driver.

2. The reconfigurable nonlinear rotary series elastic actuator with adjustable stiffness according to claim 1, characterized in that: The input ring (3) and the output ring (6) are coaxially arranged and coupled via the linear tension spring (4), and relative rotation is achieved using the flange deep groove ball bearing (12) to reduce motion friction; the input ring (3) and the output ring (6) respectively comprise an inner ring and an outer ring; the inner ring and the outer ring are each configured with four groups of symmetrically distributed linear tension springs, with the phase angle between adjacent groups being 90°.

3. The reconfigurable nonlinear rotary series elastic actuator with adjustable stiffness according to claim 1, characterized in that: The motor fixing device (2) is designed with a positioning boss to improve assembly accuracy and structural stability when connected to the driver housing (9).

4. The reconfigurable nonlinear rotary series elastic actuator with adjustable stiffness according to claim 1, characterized in that: The adjustable anchor points (5) are evenly distributed on the output ring (6) and are used to change the initial deflection angle of the linear tension spring (4), thereby giving the reconfigurable nonlinear rotational series elastic actuator an adjustable stiffness characteristic. The adjustable anchor points (5) are designed based on geometric parameters, and the axial space spring array can achieve rapid switching of stiffness modes without hardware reconstruction, thereby achieving multi-modal stiffness characteristics from nonlinear to quasi-linear, covering all working conditions from compliant interaction to high dynamic loads.

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