Robot Arm Actuator

Abstract

The present invention provides a tubular casing; an output shaft extending within the tubular casing; a motor mounted in a tubular casing; an input connector located outside the tubular casing; - an output connector located within the tubular casing, the output connector being connected to the input connector by an electrical connection means; Equipped with the connecting means comprises a rotary manifold and the output shaft is hollow; The present invention relates to an actuator for a robot arm (110).

Description

[Technical Field]

[0001] The field of the invention is that of the design and manufacture of cobotic systems.

[0002] More particularly, the present invention relates to actuators, especially but not exclusively, for robotic arms. [Background technology]

[0003] Robotic arms can be used for a variety of tasks.

[0004] One of these tasks is assisting people with physical disabilities.

[0005] Some physical disabilities reduce a person's ability to use their arms to grasp and move objects.

[0006] Cobots (collaborative robots) is the name given to robotic limbs designed to interact with users; cobots are used to enable physically disabled people to regain autonomy in their movements.

[0007] For example, a robotic arm may be mounted on a wheelchair to enable the wheelchair user to grasp and manipulate objects when the wheelchair user's own arms are unable to do so.

[0008] The patent document published as European Patent Application Publication No. EP2355958 discloses a robotic arm that is adaptable to a wheelchair.

[0009] Known robotic arms have multiple sections that are articulated together.

[0010] The connection is in particular formed by an actuator.

[0011] Conventionally, the actuator comprises a motor associated with a gearbox.

[0012] The motors allow the two sections to move relative to each other, and the gearbox allows the torque provided by the motors to be increased to increase the strength of the robot arm.

[0013] However, the actuators used have a number of drawbacks.

[0014] First, the actuator is limited in terms of the degree of freedom of the actuator.

[0015] In other words, when several actuators are mounted on a robot arm, the actuators are arranged consecutively from a first end to a second end of the arm.

[0016] Therefore, the cables designed to supply energy and commands to the actuators must pass through the robot arm.

[0017] Therefore, the rotation of the link is limited to avoid the risk of twisting and tangling of the cable.

[0018] This therefore complicates programming as it is necessary to ensure that particular orientations of particular sections are maintained when moving the robotic arm, whilst limiting the range of movement of the arm to avoid interfering with a person moving around the robotic arm.

[0019] For example, when the object being grasped at the end of a robotic arm is a glass or an open bottle, it is necessary to maintain the orientation of the glass or bottle constant or to allow movement of the glass or bottle without substantially spilling its contents.

[0020] Depending on the starting position of the arm when gripping the glass or bottle, movement may prove difficult.

[0021] Second, the robotic arm must have a suitable appearance and footprint when mounted on the wheelchair. Additionally, the robotic arm must be lightweight and consume little energy to reduce the size of the wheelchair's battery.

[0022] Therefore, the size of the linkage limits the power generated by the actuator.

[0023] Indeed, to increase the power of an actuator without excessively increasing the cost of the actuator, one widely used solution is to increase the size of the actuator, particularly the motor and / or gearbox.

[0024] However, increasing the size of the actuator directly affects the appearance and use of the robot arm, and also affects the performance of the robot arm.

[0025] At the expense of appearance and footprint, the robotic arm is made to suit the desired use.

[0026] Third, actuators need to be maintained over their lifespan.

[0027] This maintenance is particularly time consuming, expensive and tedious due to the large number of parts involved in the actuator.

[0028] In order to maximize the ratio between the power generated and the weight of the actuator, many wearing parts, such as bearings, are used.

[0029] As the name suggests, these wear parts wear out as the robot arm is used, so maintenance is necessary, but this is problematic as it requires the robot arm to be out of service for long periods of time in addition to the maintenance costs. Summary of the Invention

[0030] In particular, the object of the present invention is to overcome the drawbacks of the prior art.

[0031] More particularly, the present invention aims to provide an actuator for a robotic arm, the design of which allows for reducing the weight and size of the actuator while increasing the power generated by the actuator.

[0032] It is a further object of the present invention to provide an actuator that makes it possible to achieve a linkage with a greater range of motion than in the prior art.

[0033] It is a further object of the present invention to provide an actuator that is more reliable and easier to maintain than prior art actuators.

[0034] These and other objects described below are achieved by a robot arm actuator according to the present invention, which comprises: a tubular casing extending along a main axis; an output shaft extending within the tubular casing along a main axis; a gearbox coupled to the output shaft; a motor mounted in a tubular casing, the motor comprising a stator integrated in the tubular casing and a rotor coupled to a gearbox; an input connector located outside the tubular casing; - an output connector located within the tubular casing, the output connector being connected to the input connector by an electrical connection means; Equipped with the connecting means comprising a rotating manifold and the output shaft being hollow to allow passage of a cable connecting the connecting means to a device external to the actuator; and The actuator comprises a means for rotatably guiding the output shaft, interposed between the output shaft and a tubular casing, the guiding means comprising a first member and a second member, the motor and gearbox being located between the first member and the second member, the tubular casing comprising three connected portions along a main axis including a central portion, a first side portion and a second side portion, the central portion being received between the first side portion and the second side portion, each side portion having a shoulder for receiving the guiding means, the first side portion comprising a conical support which narrows as it extends in the direction of the main axis, the shoulder of the first side being located at a distal end of the conical support having a smaller diameter.

[0035] The use of a hollow output shaft combined with the presence of a rotary connector allows the actuator to be more compact than prior art actuators.

[0036] This further benefits the weight of the actuator, which improves the weight to power ratio compared to prior art actuators.

[0037] Additionally, the use of a hollow shaft and rotating manifold allows several actuators to be mounted serially on the robot arm, while allowing the two parts of the arm to rotate and pivot relative to each other.

[0038] In fact, the risk of cable kinking is eliminated by routing the cable inside the output shaft, and this also reduces the restriction of the movement of the arm to which the actuator is attached, since there is no risk that the cable will become an obstacle to the mobility of the arm.

[0039] Rotational guide means prevent bending of the output shaft which could result in damage to the actuator.

[0040] Additionally, the guide means makes the actuator reliable.

[0041] Due to the arrangement of the motor and gearbox, the output shaft is guided near its end, which further reduces the risk of bending.

[0042] The conical support makes it possible to limit the size of the first guide member, which in turn limits the weight of the actuator, which has advantages for the area occupied by the actuator, which in turn has advantages for the appearance of the robot arm, which can be made more compact.

[0043] According to one advantageous aspect, the actuator further comprises a stress sensor configured to know the force applied to the output shaft at any instant of time.

[0044] In particular, this makes it possible to track the activity of the actuator and to identify the stresses in the linkage to which the actuator is mounted.

[0045] According to another advantageous aspect, the stress sensor is integrally attached to the tubular casing.

[0046] This allows easy access to the stress sensor for maintenance if required.

[0047] Furthermore, by being integrated into the tubular casing, it is not affected by any movements that may be undesirable to the data being acquired.

[0048] According to another advantageous aspect, the second cap is integral with the output shaft and the second member is interposed between the second cap and the second side portion.

[0049] This further increases the adaptability of the actuator when required.

[0050] In practice, it may be necessary to adapt the actuator to specific needs. Changing the second cap quickly achieves this.

[0051] According to another advantageous aspect, at least one of the first member and the second member is a bearing.

[0052] The use of bearings allows for efficient guidance in a small footprint.

[0053] According to another advantageous aspect, at least one of the first member and the second member is a slide bearing.

[0054] The use of plain bearings further reduces the weight of the actuator.

[0055] According to another advantageous aspect, the rotating manifold comprises: - a first part having at least three metal tracks; a second part having at least three brushes each intended to cooperate with one of the metal tracks; Includes:

[0056] Two tracks can furthermore be used for the transmission of power current between several actuators mounted in series, while a third track can allow the transmission of a preset current, allowing the actuators to be controlled.

[0057] The invention further relates to a robotic arm comprising at least two sections articulated to one another.

[0058] Compared to prior art robotic arms, the robotic arm according to the present invention offers better strength for less, or at least the same, weight.

[0059] Other characteristics and advantages of the invention will be more clearly understood from reading the following description of preferred embodiments of the invention, given as illustrative and non-exhaustive examples, and from the accompanying drawings described below. [Brief explanation of the drawings]

[0060] [Figure 1] 1 is a diagram of a wheelchair with a robotic arm having at least one joint formed by an actuator according to the present invention; FIG. [Figure 2] 1 is a perspective view of an actuator according to the present invention; [Figure 3] 1 is a longitudinal cross-sectional view of an actuator according to the invention; [Figure 4] 1 is a simplified exploded view of an actuator according to the present invention; [Figure 5] 1 is a longitudinal cross-sectional view of an exploded view of the tubular casing of an actuator according to the present invention; [Figure 6] 1 is a longitudinal section of an electric rotary manifold of an actuator according to the invention, the circular view being an enlarged view showing a detail. DETAILED DESCRIPTION OF THE INVENTION

[0061] Figure 1 shows a wheelchair 100 fitted with a robotic arm 110 comprising at least one actuator 1 according to the invention (illustrated by Figures 2 to 6). The actuator 1 according to the invention is used in particular to form a joint 120 of the robotic arm 110.

[0062] More specifically, the actuator 1 is used to form a joint 120 between two sections of the robot arm 110 .

[0063] FIG. 2 shows an actuator 1 according to the invention.

[0064] Actuator 1 is - a tubular casing 2; - an output shaft 3; a gearbox 4 coupled to an output shaft 3; - Motor 5 and - input connector 6; an output connector 7 located within the tubular casing 2 and connected to the input connector by electrical connection means; Equipped with.

[0065] As shown in FIG. 3, the tubular casing extends along a major axis A.

[0066] Still referring to FIG. 3, the output shaft 3 is hollow and extends along a main axis A within the tubular casing 2 .

[0067] The hollowness of the output shaft 3 allows the passage of a cable C which connects the connection means to a device external to the actuator 1, as will be described below.

[0068] The motor 5 is mounted within the tubular casing 2 .

[0069] More specifically, the motor 5 comprises a stator 501 integrated into the tubular casing 2 and a rotor 502 coupled to the gearbox 4 .

[0070] The coupling of the rotor 502 to the gearbox 4 makes it possible to vary the rotational speed of the output shaft 3 relative to the rotational speed of the motor 5 .

[0071] As can be seen in FIG. 3, the stator 501 includes electrical coils 503, and the rotor 502 includes a plurality of magnets 504 designed to cooperate with the magnetic field generated by the coils 503 of the stator 501 to rotate the rotor 502.

[0072] 3, the inlet connector 6 is located outside the tubular casing 2, while the outlet connector 7 is located inside the tubular casing 2. More specifically, the output connector 7 is located inside the output shaft 3.

[0073] The connection means comprises a rotating manifold 8 .

[0074] The use of a rotating manifold 8 makes it possible to eliminate or avoid twisting of the cables C passing through the actuators 1, in particular for the mounting of several actuators 1 in series.

[0075] Referring to FIG. 6, the rotary manifold 8 includes: - a first part 801 having at least three metal tracks (pistes, rails) 802; a second part 803 having at least three brushes 804 each designed to cooperate with one of the metal tracks 802; Includes:

[0076] Two metal tracks 802 may be specifically allocated for the passage of a power supply current making it possible to power several actuators 1 mounted in series.

[0077] A third metal track of the metal tracks 802 may be used for the passage of a control current for controlling the actuator 1 .

[0078] Other metal tracks 802 may be provided specifically to allow control currents to be transmitted to other actuators 1 .

[0079] As shown by FIGS. 3 and 4, the actuator 1 further comprises means for rotatably guiding the output shaft 3 .

[0080] These guide means are inserted between the output shaft 3 and the tubular casing 2 .

[0081] More specifically, the rotational guide means comprises a first member 9 and a second member 10 .

[0082] The first member 9 and the second member 10 are arranged such that the motor 5 and the gearbox 4 are located between the first member 9 and the second member 10 .

[0083] This is beneficial for the compactness of the actuator 1 and its ability to guide the rotation of the output shaft 3 .

[0084] According to one embodiment, at least one of the first member 9 and the second member 10 is a bearing.

[0085] According to the embodiment illustrated by Figure 3, each of the first member 9 and the second member 10 is a bearing. The bearings may be ball bearings, needle bearings, tapered roller bearings, angular contact ball bearings, or any other type of bearing.

[0086] As an alternative not shown, at least one of the first member 9 and the second member 10 is a plain bearing.

[0087] The rotational guide means may comprise, for example, another member 11 inserted between the output shaft 3 and the rotor 502 .

[0088] 4 and 5, the tubular casing 2 comprises at least three connected sections along a major axis A.

[0089] More precisely, the tubular casing 2 comprises a central portion 201 , a first side portion 202 and a second side portion 303 .

[0090] The central portion 201 is received between the first side portion 202 and the second side portion 203 .

[0091] Each side 202, 203 is provided with a shoulder 204 for receiving a guide means.

[0092] 5, the first side 202 comprises a conical support 205 that extends towards the inside of the tubular body 2, i.e., narrows in the direction of the main axis A, and the shoulder 204 is applied within the conical support 205. More specifically, the shoulder 204 of the first side 202 is located at the distal end of the conical support 205, which has a smaller diameter.

[0093] Referring to the exploded view of FIG. 4, the tubular casing 2 is closed at a first end 206 by a first cap 207 and at a second end 208 by a second cap 209 .

[0094] The first cap 207 and the second cap 209 make it possible to seal the actuator 1 from any dust or contaminants that may impair the proper operation of the actuator 1 and result in maintenance intervention, such as requiring the robot arm 110 containing the abnormal actuator 1 to be taken out of service.

[0095] To facilitate assembly and maintenance of the actuator 1, the second cap 209 is integral with the output shaft 3.

[0096] As shown by FIG. 3, the second member 10 is further inserted between the second cap 209 and the second side 203 of the tubular casing 2 .

[0097] According to the embodiment illustrated by Figure 3, the actuator 1 further comprises a stress sensor 11. The stress sensor 11 is integrally mounted with the tubular casing 2 and is configured to detect the force applied to the actuator 1, and in particular the force applied to the output shaft 3, at any given time.

[0098] The sensor 11 may also be connected to the rotary manifold 8 for exchanging data with a remote control unit.

[0099] By way of illustrative and non-exhaustive example, the sensor 11 is a stress gauge.

[0100] In operation, the motor 5 rotates the output shaft 3 .

[0101] The gearbox 4 makes it possible to vary the torque supplied by the output shaft 3 according to the torque generated by the motor 5 .

[0102] Information and power can be transferred between multiple actuators 1 mounted serially on the robot arm 110 due to the presence of a rotating manifold 8 .

[0103] In fact, the cable passes through the hollow output shaft 3, so that the cable remains twist-free.

[0104] As a result, the cable is not subjected to any torsion caused by the rotation of the output shaft 3 .

[0105] Furthermore, the weight to power ratio provided by the just described actuator 1 is greater than the weight to power ratio of prior art actuators.

[0106] This is partly due to the reduced space requirements of the developed structures and individual parts.

[0107] By way of example, the structure of the actuator according to the present invention can provide approximately 15% space savings in diameter and approximately 20% space savings in length compared to prior art actuators, while also achieving a weight reduction of more than 10%.

[0108] Tests have further shown that, despite its smaller dimensions and weight than prior art actuators, the actuator 1 according to the invention: - 50% more continuous torque, - Approximately 13% higher maximum torque, - 265% faster maximum output shaft speed, Demonstrate that it is possible to bring about

Claims

1. An actuator (1) for a robot arm (110), comprising: a tubular casing (2) extending along a main axis (A); an output shaft (3) extending along said main axis (A) within said tubular casing (2); a gearbox (4) coupled to said output shaft (3); a motor (5) mounted on said tubular casing (2), said motor (5) comprising a stator (501) integrated in said tubular casing (2) and a rotor (502) connected to said gearbox (4); an input connector (6) located outside said tubular casing (2); an output connector (7) located inside said tubular casing (2) and connected to said input connector (6) by electrical connection means; An actuator (1) comprising: the connecting means comprises a rotary manifold (8), the output shaft (3) being hollow to allow the passage of a cable (C) connecting the connecting means to a device external to the actuator (1); The actuator (1) comprises a means for rotatably guiding the output shaft (3) inserted between the output shaft (3) and the tubular casing (2), the guiding means comprising a first member (9) and a second member (10), the motor (5) and the gearbox (4) are located between the first member (9) and the second member (10), and the tubular casing (2) comprises the main shaft (A) including a central portion (201), a first side portion (202), and a second side portion (203). the central part (201) is received between the first side part (202) and the second side part (203), each side part (202, 203) having a shoulder (204) for receiving the guiding means, the first side part (202) having a conical support (205) tapering as it extends in the direction of the main axis (A), the shoulder (204) of the first side part (202) being located at the distal end of the conical support (205) having a smaller diameter. Actuator (1).

2. the actuator (1) further comprises a stress sensor (11) configured to detect the force applied to the output shaft (3) at any instant of time; An actuator (1) according to claim 1.

3. The stress sensor (11) is mounted integrally with the tubular casing (2). The actuator according to claim 2 .

4. At least one of the first member (9) and the second member (10) is a bearing. An actuator (1) according to any one of claims 1 to 3.

5. At least one of the first member (9) and the second member (10) is a plain bearing. An actuator (1) according to any one of claims 1 to 4.

6. The rotary manifold (8) a first part (801) with at least two metal tracks (802); a second part (803) with at least three brushes (804) each designed to cooperate with one of said metal tracks (802); characterized in that it comprises An actuator (1) according to any one of claims 1 to 5.

7. A robot arm (110) comprising at least two sections articulated to one another by an actuator (1) according to any one of claims 1 to 6.

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