Torque hub motor

Abstract

The utility model discloses a torque wheel hub motor, which comprises a wheel hub motor and a sensor group arranged on the side surface of the wheel hub motor and connected with a tower footing, the output of the sensor group at least comprises a group of torque signal sensors for sampling the input torque of a chain and the driving state of the wheel hub motor and transmitting signals to a signal processing unit; the signal processing unit obtains input torque signals, speed signals and clutch overrunning signals and carries out judgment and calculation, the motor driving unit controls operation of a motor through control signals output by the signal processing unit, common driving of input torque and motor output is achieved, and the torque sensor and the controller are integrated in the motor. The integrated level of the motor is improved, the assembly process of the whole vehicle is simplified, and riding is safer and more comfortable by jointly controlling the torque signal, the speed signal and the override signal and optimizing the control algorithm.

Description

Technical Field

[0001] The utility model relates to the field of motors, in particular to a torque hub motor. Background Art

[0002] The motor is one of the most common power devices. After a hundred years of development, it has developed into many different types and structures and has become one of the most important equipment in daily production and life. Among them, the hub motor is widely used in the field of vehicle drive due to its simple structure, reliable performance and low cost, especially in commuter vehicles such as electric vehicles and electric-assisted bicycles. The existing hub motor does not have integrated sensors and usually needs to be used with a central axis sensor, which reduces the system integration. At the same time, the motor drive algorithm lacks high-integration hub motors with sensors and is not suitable for rear hub motor drives with torque sensors. Utility Model Content

[0003] In view of the defects of the above-mentioned prior art, the main purpose of the utility model is to overcome the shortcomings of the prior art and discloses a torque hub motor, including a fixed seat, a rotor, and a stator winding and a hub coaxially arranged on the fixed seat, the stator winding is fixedly connected to the fixed seat, the rotor is coaxially arranged and rotationally connected to the stator winding, and the hub is rotationally connected to the fixed seat; the rotor is used to directly or indirectly drive the hub to rotate; the tower base is rotationally connected to the wheel hub through a clutch, and a sensor group is arranged between the tower base and the wheel hub, and the sensor group is used to collect torque signals and clutch overrunning signals.

[0004] Furthermore, the fixing seat is an integrated shaft, and both ends of the integrated shaft are provided with fixed ends, and the fixed ends are fixedly connected to the frame.

[0005] Furthermore, fixing sleeves are arranged at both ends of the integrated shaft, and fixing parts cooperating with the vehicle frame are arranged on the fixing sleeves.

[0006] Furthermore, a groove is provided on the surface of the integral shaft, and the signal line of the sensor group is routed through the groove.

[0007] Furthermore, a fixed end is provided at the end of the integral shaft.

[0008] Furthermore, clamps are provided at both ends of the integral shaft.

[0009] Furthermore, the sensor group also collects speed signals.

[0010] Furthermore, the clutch overrunning signal is collected from a magnetic sensor or a switch signal.

[0011] Further, the magnetic sensor is arranged on the wheel hub, and a magnet is arranged at a corresponding position of the circumference of the gear ring; or the magnetic sensor is arranged on the gear ring, and a magnet is arranged at a corresponding position of the circumference of the gear ring; or the magnetic sensor is arranged on the tower base, and a magnet is arranged outside the corresponding position of the circumference of the wheel hub; or the magnetic sensor is arranged on the wheel hub, and the magnet is arranged on the outer circumferential surface of the tower base.

[0012] Furthermore, the torque signal is collected by a torque sensor; the torque sensor includes a torque collection structure and a processing circuit; the torque collection structure includes a torsion plate and a strain gauge, the torsion plate includes a disc body having at least one torsion plate, the center of the disc body is coaxially arranged with the wheel hub, the torsion plate is floatingly connected to the wheel hub, the center of the disc body is rotatably set on the fixed seat, and the wheel hub is connected to the tower base.

[0013] Furthermore, a limiting plate is radially protruded on the disc body, and the limiting plate is floatingly connected to the wheel hub.

[0014] Furthermore, the output signal of the sensor group is an analog signal and / or a digital signal and / or a bus signal.

[0015] A torque hub motor control method is used for a controller having an input circuit, a calculation control unit and a drive circuit.

[0016] a. The sensor group samples the input torque of the chain and the driving status of the hub motor and transmits the signal to the signal processing unit.

[0017] b. The signal processing unit obtains the input torque signal, speed signal and clutch overrunning signal and makes judgments and calculations; when the torque signal is lower than the threshold, the motor stops driving; when the torque signal is higher than the threshold and the speed signal is lower than the threshold and the clutch overrunning signal indicates locking, the motor calculates the output in proportion to the function according to the torque signal and drives normally; when the torque signal is higher than the threshold and the speed signal is higher than the threshold and lower than the maximum speed limit and the clutch overrunning signal indicates locking, the motor calculates the output in proportion to the function according to the torque signal and drives with reduced power according to the speed value; when the clutch overrunning signal indicates overrunning, the motor stops driving;

[0018] c. The motor drive unit controls the operation of the motor through the control signal output by the signal processing unit, thereby achieving joint drive of the input torque and the motor output.

[0019] Furthermore, in step b, the function used in the function ratio calculation is a linear function, a quadratic function or a power function.

[0020] Furthermore, in step b, the power drive is reduced according to the speed value. When the speed value is greater than the threshold and less than the maximum speed limit, the motor output torque is the input torque value*(1-(speed value-speed threshold) / (maximum speed limit-speed threshold)).

[0021] A wheelchair comprises the torque hub motor.

[0022] A scooter comprises the torque hub motor.

[0023] Beneficial effects achieved by the utility model:

[0024] 1) By integrating the torque sensor and controller into the motor, the motor integration level is improved and the vehicle assembly process is simplified.

[0025] 2) By integrating the torque sensor in the motor, the integration level is improved, the complexity of the vehicle is reduced, and better control effect is obtained.

[0026] 3) By using torque signals, speed signals and overrunning signals to jointly control the motor drive and optimize the control algorithm, riding becomes safer and more comfortable.

[0027] 4) The overrunning clutch signal is creatively added to improve the redundancy of signal control and enhance the reliability and safety of control.

[0028] 5) The torque sensor uses a disc body and a radially protruding torsion plate to achieve transmission and variable acquisition, with a compact structure and easy installation. A limit plate is added to protect the torsion plate and prevent damage to the torque sensor caused by excessive deformation; in addition, the limit plate can be set to reduce the strength of the torsion plate and make the deformation more linear. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a side sectional view of a torque hub motor of the utility model;

[0030] Figure 2 It is a side sectional view of a torque hub motor with a fixed seat as an integrated shaft structure;

[0031] Figure 3 for Figure 2 Schematic diagram of the three-dimensional structure;

[0032] Figure 4 It is a side view of the torque sensor and the tower base;

[0033] Figure 5 for Figure 4 Middle AA section view;

[0034] Figure 6 for Figure 4 Explosion diagram of

[0035] Figure 7 It is a structural schematic diagram of an integrated shaft;

[0036] Figure 8 for Figure 7 A structural diagram from another perspective;

[0037] Fig. 9 It is a schematic diagram of an algorithm flow of a torque hub motor control method of the utility model;

[0038] The reference numerals are as follows:

[0039] 1. Fixed seat, 2. Sensor group, 3. Tower base, 4. Stator winding, 5. Rotor, 6. Reduction group, 7. Wheel hub, 8. Magnet, 9. Torque plate, 10. Input plate, 11. Integrated shaft, 12. Fixed end, 13. Fixed sleeve, 14. Permanent magnet, 15. Wiring groove, 91. Disc body, 92. Torsion plate, 93. Limit plate, 101. Drive groove, 102. Limit groove, 111. Protrusion. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0041] A torque hub motor, such as Figure 1-Figure 8 As shown, it includes a fixed base 1, a rotor 5, and a stator winding 4 and a hub 7 coaxially arranged on the fixed base 1, the stator winding 4 is fixedly connected to the fixed base 1, the rotor 5 is coaxially arranged and rotationally connected to the stator winding 4, and the hub 7 is rotationally connected to the fixed base 1; the rotor is used to directly or indirectly drive the hub 7 to rotate; the tower base 3 is rotationally connected to the hub 7 through a clutch, and a sensor group 2 is arranged between the tower base 3 and the hub 7, and the sensor group 2 is used to collect torque signals and clutch overrunning signals.

[0042] The rotor 5 is half-wrapped on the outside of the stator winding, and the output end of the rotor 5 is connected to the input end of the planetary reduction group 6, and the output end of the rotor 5 is connected to the hub 7 of the hub motor through an overrunning clutch.

[0043] The freehub base 3 is unidirectionally rotatably connected to the wheel hub 7 via a ratchet clutch, and a sensor group 2 arranged between the freehub base 3 and the wheel hub 7 includes a torque sensor and a magnetic sensor.

[0044] The wheel hub 7 is connected to the tower base 3 through a torque collection structure, which is arranged in the wheel hub motor or in the tower base 3. The torque collection structure is connected to a processing circuit and constitutes a torque sensor together with the processing circuit. The processing circuit can be arranged on the side of the reduction group 6 of the wheel hub motor, or in the tower base 3, and of course can also be arranged on the stator of the wheel hub motor.

[0045] The torque collection structure can be a torque arm, a torque spoke or a torque plate that is input by the tower base 3 and transmits the wheel hub 7. Strain gauges or magnetic materials are attached to appropriate positions of the torque arm, the torque spoke or the torque plate to collect the torque transmitted by the tower base through changes in resistance or magnetic field.

[0046] Specifically, the torque collection structure includes a torsion plate 9 having at least one torsion plate and a strain gauge, wherein the torsion plate 9 is connected to the input plate 10 of the overrunning clutch, the torsion plate 9 includes a plate body 91, the center of the plate body 91 is coaxially arranged with the wheel hub 7, the torsion plate 92 is floatingly connected with the wheel hub 7, the center of the plate body 91 is rotatably arranged on the fixed seat 1, and the wheel hub 7 is connected to the tower base 3. Specifically, the torsion plate 92 is radially extended from the side of the plate body, a driving groove 101 matching the torsion plate is recessed on one side wall of the input plate 10, and the strain gauge is adhered to the torsion plate 91; the torsion plate 9 is rotatably arranged on the fixed seat 1. When driving, the pedaling force is transmitted to the torsion plate 9 through the tower base 3. The torsion plate 9 transmits the power to the input plate 10 of the overrunning clutch through the torsion plate 92, and the deformation degree of the torsion plate 92 is collected through the strain gauge to obtain the torque value.

[0047] The floating connection is defined as a connection mode in which there is a gap at the mating position and the connection can rotate relative to each other, that is, there is a gap in the circumferential direction of the torsion plate 92 and the driving slot 101 .

[0048] In the above embodiment, if Figure 1-Figure 8 As shown, a limit plate 93 is radially provided on the side of the disk body 91, and a limit groove 102 cooperating with the limit plate 93 is recessed on one side wall of the input disk 10. The limit plate 93 and the limit groove 102 cooperate with each other to protect the torsion plate 92 to prevent irreversible deformation caused by excessive deformation. A gap is provided between the limit plate 93 and the limit groove 102, which is usually set to 0.5mm-1mm. In addition, the number of limit plates 93 can be set according to actual needs, and can be one, two or even more; and the limit plates 93 and the torsion plates 92 can be distributed at equal intervals or at unequal intervals. If the torsion plate 91 has sufficient strength, a limit plate may not be provided.

[0049] In the above embodiment, by providing the limit plate 93, the thickness of the torsion plate 92 can be reduced, so that the strain gauge acquisition is more linear, thereby ensuring that the voltage width of the acquisition signal reaches 50mv / Nm.

[0050] Normally, the torsion plate 92 does not contact the wheel hub 7. When the disk body 91 is driven, the disk body 91 can rotate relatively freely until the torsion plate 92 contacts the inner wall of one side of the driving slot 101 and starts to transmit torque. At this time, the deformation is collected and the torque is calculated through the strain gauge set on the torsion plate 92.

[0051] To ensure safety, the input part of the torque sensor is provided with a one-way transmission structure, which is arranged between the torsion plate 9 and the tower base 3, so that the tower base 3 can only drive the torsion plate 9 in one direction.

[0052] In this embodiment, Figure 1-Figure 8 As shown, the one-way transmission structure is a ratchet. Of course, the one-way transmission structure can be a one-way bearing 8, an overrunning clutch, or a roller wedge, which is not limited here.

[0053] In one embodiment, if Figure 1-Figure 8 As shown, the fixing seat 1 is an integral shaft.

[0054] In one embodiment, if Figure 1-Figure 8 As shown, a groove 15 is provided on the surface of the integral shaft 11, and the signal line of the sensor group 2 is routed through the groove 15. The integral shaft 11 is fixed to the vehicle frame and remains relatively still, and the signal line is placed in the groove 15 to achieve hidden installation and avoid confusion in internal routing.

[0055] In a specific embodiment, if Figure 1-Figure 8 As shown, both ends of the integrated shaft 11 are provided with fixed ends 12, and the fixed ends 12 are fixed to the rear fork of the frame, and the two fixed ends 12 of the integrated shaft 11 extend from both sides of the wheel hub 7 of the motor. Among them, the fixed end 12 is a plane set on the end surface of the integrated shaft 11, which is connected to the rear fork of the frame through the plane to achieve a quick connection between the integrated shaft 11 and the frame, and to achieve the stop of the integrated shaft 11. During assembly, insert from one end of the stator winding 4 so that both ends of the integrated shaft 11 protrude from the wheel hub 7. After being assembled in place, the integrated shaft 11 is fixed to the stator winding 4. Among them, a convex portion 111 is radially provided on the integrated shaft 11, and the convex portion is fixedly connected to the stator winding 4 by screws.

[0056] The integral shaft 11 can be designed as an axial structure integrated with the core support of the stator winding 4, or can be set as a separate axial structure and fixedly connected to the stator by means of screws, toothed structures, threads or tenons.

[0057] When the integrated shaft 11 is a separate shaft-shaped structure, the integrated shaft 11 becomes the inner sleeve of the hub 7 , and the hub 7 is rotatably fixed on the inner sleeve. The inner sleeve can also be provided with a flange and fixedly connected to the stator winding 4 by the flange.

[0058] It should be noted that the shaft length of the integral shaft 11 is equal to or longer than the length of the motor body.

[0059] The outer side of the rotor 5 is covered with a hub 7 , which is coaxially arranged with the rotor 5 and rotatably connected to the integral shaft 11 .

[0060] Usually, the connection is achieved by means of bearings, the hub wraps the rotor 5 and the stator winding inside, and the rotor 5 is fixed to the hub 7. A more common practice is to directly use the hub 7 as the rotor 6 of the movement, that is, a permanent magnet 14 is directly attached to the inner side of the hub 7.

[0061] In the above embodiment, both ends of the integrated shaft 11 are also sleeved with a clamping piece. In this embodiment, the clamping piece is a fixing sleeve 13, and the integrated shaft 11 is fixedly connected to the frame through the fixing sleeve 13 and stops rotation. Stopping planes are provided at both ends of the integrated shaft 11, and the fixing sleeve 13 is axially recessed with a mounting hole that matches the end of the integrated shaft 11. During assembly, the fixing sleeve 13 only needs to be inserted into the integrated shaft 11 to complete the installation. Through the setting of the fixing sleeve 13, the fixing sleeve 13 only needs to select a shape that matches the frame, so that the integrated shaft 11 can be fixed to frames of more different sizes.

[0062] In particular, in a special case in the present embodiment, the integrated shaft 11 is a barrel shaft, and the axial positions of the stator winding 4 and the hub 7 of the motor are both provided with through holes, which are coaxially arranged, and the barrel shaft passes through the holes at the axial positions of the stator winding 4 and the hub 7 of the motor, and the shaft length of the barrel shaft is equal to or longer than the length of the motor body, and the length of the motor body is the distance between the axial fixed end 12 of the motor housing and the fixing sleeve 13 at the end of the tower base 3 at the other end of the motor housing. At this time, the motor realizes the anti-rotation fixation of the motor and the frame through the fixed end 12 and the fixing sleeve 13, and the motor is locked to the frame through the barrel shaft, thereby realizing the fixation of the motor.

[0063] In one embodiment, the sensor group 2 also carries a group of speed signals and a group of clutch overrunning signals. The speed signals are collected by speed measuring magnetic points and magnetic sensors arranged outside the wheel hub 7, and can also be obtained by collecting speed measuring magnetic points arranged inside the wheel hub motor, or even by collecting the signals of the rotor 5 magnet 8 of the wheel hub motor; the clutch overrunning signal of the sensor is obtained by collecting the relative motion state of the tower base 3 and the wheel hub 7; when in the driving state, the clutch is locked, and the tower base 3 rotates synchronously with the wheel hub 7; when the wheel hub 7 is in the gliding state, there is a speed difference between the tower base 3 and the wheel hub 7, and at this time, the working state of the clutch can be obtained by collecting the signals of the speed measuring magnet 8 arranged on the wheel hub 7; of course, the working state of the clutch can also be obtained by a pressure switch or a micro switch, which is not limited here.

[0064] As an extension of the above-mentioned embodiment, the magnet 8 for measuring the working state of the overrunning clutch can be arranged on the sprocket, and the magnetic sensor for detecting the position of the magnet 8 can be arranged on the wheel hub 7 or at a position corresponding to the magnet 8 in the wheel hub 7; of course, the magnet 8 can also be arranged on the wheel hub 7, and the magnetic sensor for detecting the position of the magnet 8 can be arranged on the sprocket at a position corresponding to the magnet 8; in addition, the magnet 8 can also be arranged on the wheel hub 7, and the magnetic sensor for detecting the position of the magnet 8 can be arranged on the tower base 3 at a position corresponding to the magnet 8, or the magnet 8 can be arranged on the tower base 3, and the magnetic sensor for detecting the position of the magnet 8 can be arranged on the wheel hub 7 at a position corresponding to the magnet 8.

[0065] It should be noted that when the magnet 8 is set on the gear disk and the sensor is set in the wheel hub 7, the material used for the wheel hub 7 is non-magnetic or weakly magnetic material such as aluminum or aluminum alloy; or, a window is opened at the sensor position of the wheel hub 7 to ensure normal collection of magnetic signals.

[0066] The magnetic sensor mentioned above can be a coil induction type, a Hall induction type or a reed switch type sensor.

[0067] In particular, the motor may also be integrated with a motor controller, which is disposed on one side of the stator of the motor and fixedly connected to the stator. In addition, the controller may also be disposed on the outside of the motor and connected to the fixing seat 1 of the motor.

[0068] The utility model also discloses a control method for the torque hub motor. Fig. 9 As shown, a controller having an input circuit, a calculation control unit and a drive circuit,

[0069] a. The sensor group samples the input torque of the chain and the driving status of the hub motor and transmits the signal to the signal processing unit.

[0070] b. The signal processing unit obtains the input torque signal, speed signal and clutch overrunning signal and performs judgment and calculation;

[0071] c. The motor drive unit controls the operation of the motor through the control signal output by the signal processing unit, thereby achieving joint drive of the input torque and the motor output.

[0072] In step b, when the torque signal is lower than the threshold, the motor stops driving regardless of whether the output states of the speed signal and the clutch overrunning signal are within the set range;

[0073] When the torque signal is higher than the threshold and the speed signal is lower than the threshold and the clutch overrun signal indicates locking, the motor performs function ratio calculation output according to the torque signal and drives normally. The function used in the function ratio calculation is a linear function, such as the motor output torque and the sensor torque are 1:1, a quadratic function, such as the sensor torque and the motor output torque are (X / 10) times the square, or a power function relationship with a larger motor main force ratio;

[0074] When the torque signal is higher than the threshold and the speed signal is higher than the threshold and lower than the maximum speed limit, and the clutch overrun signal indicates locking, the motor calculates the function ratio output according to the torque signal and reduces the power drive according to the speed value. When the speed value is greater than the threshold and less than the maximum speed limit, the motor output torque is the input torque value * (1-(speed value-speed threshold) / (maximum speed limit-speed threshold)); for example, assuming that the speed threshold is 20Km / h and the maximum speed limit is 25Km / h, when the speed is lower than 20Km / h, the normal driving state is that the torque signal is 40N*m and the motor output torque is also 40N*m. m, when the speed value is greater than the threshold value and less than the maximum speed limit value, for example, when the speed is 21Km / h, the ratio of the speed value greater than the threshold value is (21-20) / (25-20)=20%, and the motor output is 80% of the normal state, that is, when the torque signal is 40N*m, the motor output torque is also 32N*m, when the speed is 22Km / h, the ratio of the speed value greater than the threshold value is (22-20) / (25-20)=40%, and the motor output is 60% of the normal state, that is, when the torque signal is 40N*m, the motor output torque is also 24N*m, and so on;

[0075] When the clutch overrun signal indicates overrunning, the motor stops driving regardless of the torque signal size and speed signal status.

[0076] In addition, the signal processing unit also collects brake signals. When a brake signal appears, the signal processing unit immediately stops driving the motor regardless of the current status of the motor and sensor.

[0077] As mentioned above, the clutch overrunning signal is a switch signal or a pulse signal formed by the slip rate. The controller determines whether the switch signal or the pulse signal exists to know whether the overrunning clutch is disengaged.

[0078] In addition, in order to obtain a better motor driving effect, the motor driving algorithm of the calculation control unit is a FOC control algorithm or a DTC control algorithm.

[0079] The beneficial effects of the torque hub motor and the control method thereof of the utility model are as follows:

[0080] 1) By integrating the torque sensor and controller into the motor, the motor integration level is improved and the vehicle assembly process is simplified.

[0081] 2) By integrating the torque sensor in the motor, the integration level is improved, the complexity of the vehicle is reduced, and better control effect is obtained.

[0082] 3) By using torque signals, speed signals and overrunning signals to jointly control the motor drive and optimize the control algorithm, riding becomes safer and more comfortable.

[0083] 4) The overrunning clutch signal is creatively added to improve the redundancy of signal control and enhance the reliability and safety of control.

[0084] The above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. If the present invention is modified or replaced by equivalents without departing from the spirit and scope of the present invention, they should be included in the scope of protection of the claims of the present invention.

Claims

1. A torque hub motor, characterized in that: It comprises a fixing seat, a rotor, and a stator winding and a wheel hub coaxially arranged on the fixing seat, wherein the stator winding is fixedly connected to the fixing seat, the rotor is coaxially arranged and rotationally connected to the stator winding, and the wheel hub is rotationally connected to the fixing seat; the wheel hub is directly or indirectly driven to rotate by the rotor; The tower base is rotationally connected to the wheel hub through a clutch, and a sensor group is arranged between the tower base and the wheel hub, and the sensor group is used to collect torque signals and clutch overrunning signals.

2. A torque hub motor according to claim 1, characterized in that: The fixing seat is an integrated shaft, and both ends of the integrated shaft are provided with fixing ends, and the fixing ends are fixedly connected to the vehicle frame.

3. A torque hub motor according to claim 2, characterized in that: A groove is arranged on the surface of the integral shaft, and the signal line of the sensor group is routed through the groove.

4. A torque hub motor according to claim 2, characterized in that: Two ends of the integrated shaft are provided with fixing sleeves, and the fixing sleeves are provided with fixing parts matched with the vehicle frame.

5. The torque hub motor according to claim 1, characterized in that: The clutch overrunning signal is collected from a magnetic sensor or a switch signal.

6. A torque hub motor according to claim 5, characterized in that: The magnetic sensor is arranged on the wheel hub, and a magnet is arranged at a position corresponding to the circumference of the gear ring; or the magnetic sensor is arranged on the gear ring, and a magnet is arranged at a position corresponding to the circumference of the gear ring; or the magnetic sensor is arranged on the tower base, and a magnet is arranged outside the corresponding position of the circumference of the wheel hub; or the magnetic sensor is arranged on the wheel hub, and the magnet is arranged on the outer circumferential surface of the tower base.

7. The torque hub motor according to claim 1, characterized in that: The torque signal is collected by a torque sensor; the torque sensor includes a torque collection structure and a processing circuit; the torque collection structure includes a torsion plate and a strain gauge, the torsion plate includes a disc body having at least one torsion plate, the center of the disc body is coaxially arranged with the wheel hub, the torsion plate is floatingly connected to the wheel hub, the center of the disc body is rotatably set on the fixed seat, and the wheel hub is connected to the tower base.

8. The torque hub motor according to claim 7, characterized in that: A limiting piece is radially protruded on the disc body, and the limiting piece is floatingly connected to the wheel hub.

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