Universal head device

Abstract

To provide a universal head device that is pan / tilt-driven by a DC motor of a direct drive mechanism, and is capable of suppressing deviation of pan / tilt angles caused by inertial forces or disturbances during a rotational motion.MEANS FOR SOLVING THE PROBLEM: A universal head device which can be mounted with a camera unit includes: an actuator that is a direct drive mechanism and rotates the camera unit around the rotation axis; and load means that applies a rotational load to the rotation axis in a direction that stops the rotation. The load means is characterized by applying the rotational load to the rotation axis while the actuator is being driven.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a pan head device for an imaging device that can be rotated in a panning or tilting manner. [Background technology]

[0002] PTZ cameras are a typical device suited to video distribution over the Internet. These PTZ cameras are known for their smooth and quiet drive mechanism, which is a direct drive mechanism using a DC motor. This uses a DC motor as the pan / tilt drive actuator, and the actuator is directly connected to the pan axis and tilt axis with a reduction ratio of 1:1. Because it is driven with a reduction ratio of 1:1 without using gears, there is no rattle caused by backlash in the reduction mechanism, and smooth rotation can be expected.

[0003] However, since a DC motor does not generate an excitation force when it is not energized, there is a risk that the pan angle or tilt angle may be shifted due to disturbances such as vibrations on the surface on which the imaging device is installed while the DC motor is stopped.

[0004] Therefore, Patent Document 1 discloses a technique for applying a rotational load around the rotation axis of a DC motor while the DC motor of a direct drive mechanism is stopped in order to prevent deviation of the pan angle or tilt angle while the DC motor is stopped from rotating. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-39261 Summary of the Invention [Problem to be solved by the invention]

[0006] The conventional technology disclosed in Patent Document 1 takes into consideration the holding force when the DC motor is stopped from rotating, but does not take into consideration the risk of the angle of view being shifted due to insufficient holding force while the DC motor is rotating.

[0007] Therefore, the present invention aims to provide a pan / tilt head device that uses a DC motor of a direct drive mechanism to drive pan / tilt, and that can suppress deviations in pan / tilt angles due to inertial forces or external disturbances during rotational operation. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a camera head device to which a camera unit can be attached, which is a direct drive mechanism and includes an actuator that rotates the camera unit around a rotation axis, and a load means that applies a rotational load to the rotation axis in a direction to stop the rotation, and is characterized in that the load means applies the rotational load to the rotation axis while the actuator is driving. [Effects of the Invention]

[0009] According to the present invention, a pan / tilt head device that uses a DC motor of a direct drive mechanism for pan / tilt drive can be provided that can suppress deviations in pan / tilt angles caused by inertial forces or disturbances during rotational operation. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view of a PTZ camera according to a first embodiment of the present invention. [Figure 2] 1 is a perspective view of a PTZ camera according to a first embodiment of the present invention when installed for vertical shooting. [Figure 3] 1 is a perspective view of a PTZ camera according to a first embodiment of the present invention, with the exterior removed when the camera is installed for vertical shooting. [Figure 4] 1 is a cross-sectional view showing a tilt rotation mechanism of a PTZ camera according to a first embodiment of the present invention. [Figure 5]1 is a cross-sectional view showing a pan rotation mechanism of a PTZ camera according to a first embodiment of the present invention. [Figure 6] 1 is a functional block diagram of a PTZ camera according to a first embodiment of the present invention. [Figure 7] FIG. 2 is a flowchart showing the control flow of the PTZ camera according to the first embodiment of the present invention. [Figure 8] FIG. 3 is a conceptual diagram showing the relationship between the torque of a pan motor and a pan electromagnetic brake of the PTZ camera according to the first embodiment of the present invention. [Figure 9] FIG. 10 is a flowchart showing the control flow of a PTZ camera according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a flowchart showing the control flow of a PTZ camera according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] A PTZ camera according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0012] (First embodiment) The first embodiment will be described below with reference to FIGS.

[0013] First, the configuration of a PTZ camera 100 according to an embodiment of the present invention will be described.

[0014] FIG. 1 is a perspective view showing the appearance of a PTZ camera 100. The PTZ camera 100 is, for example, a network camera, and has a camera unit 110, a second rotating unit 111, and a base unit 112. The second rotating unit 111 and the base unit 112 form a camera platform device 100a. The camera unit 110 can be attached to the camera platform device 100a. The camera unit 110 captures an image of a subject and is rotatable in a pan direction and a tilt direction. By rotating the camera unit 110 in the pan direction and tilt direction and pointing it toward the subject, it becomes possible to shoot video for video production or for live streaming.

[0015] Next, a case where the PTZ camera 100 is installed for vertical shooting will be described. Fig. 2 shows an example where the PTZ camera 100 according to an embodiment of the present invention is installed for vertical shooting using a tripod 300. The PTZ camera 100 has a mounting portion (not shown) on the bottom surface of the base portion 112, and can be attached to the tripod 300 in a state rotated 90° from the normal position. In this way, the state where the PTZ camera 100 is installed in a position tilted 90° from the normal position is an installation for vertical shooting.

[0016] Here, two types of shooting modes, a normal shooting mode and a vertical shooting mode, are prepared for the PTZ camera 100. The PTZ camera 100 is equipped with an acceleration sensor 180 (not shown) on the base unit 112, and acquires output (information) from the acceleration sensor 180 to estimate the attitude of the PTZ camera 100. When the acceleration sensor 180 detects that the attitude has changed from the normal attitude to an attitude for vertical shooting tilted by 90 degrees, the shooting mode transitions from the normal shooting mode to the vertical shooting mode.

[0017] Next, the tilt rotation mechanism of PTZ camera 100 according to the embodiment of the present invention when it is in a position for vertical shooting will be described with reference to Figures 3 and 4. Figure 3 is a perspective view of PTZ camera 100 according to the embodiment with the exterior removed when it is installed for vertical shooting. Figure 4 is a cross-sectional view of the tilt rotation mechanism of PTZ camera 100 according to the embodiment at first rotation axes 115A and 115B.

[0018] 3 and 4, lens 113 inside camera unit 110 is supported by lens barrel support member 114. Lens barrel support member 114 is supported at both ends by pan base 116 inside second rotating unit 111 via bearing members 117A and 117B so as to be tilt rotatable. As a result, camera unit 110 is supported around first rotating shafts 115A and 115B with respect to second rotating unit 111.

[0019] Here, the rotation of the camera unit 110 in the tilt direction is performed by a first motor 120 (tilt motor) serving as an actuator. The first motor 120 is directly connected to the first rotation shafts 115A and 115B, and can rotate the camera unit 110 in the tilt direction at a reduction ratio of 1:1. The first motor 120 is a DC brushless motor, and is tilt-driven by a direct drive mechanism. The first motor 120 is used for tilt drive in the normal position, and for pan drive when installed for vertical shooting.

[0020] A first electromagnetic brake 121 is connected to the first rotation shaft 115B. The first electromagnetic brake 121 applies a rotational load to the first rotation shaft 115B in a direction to stop rotation. The first electromagnetic brake 121 is a rotational load mechanism that is excited and activated when energized. This makes it possible to apply a rotational load as a frictional load in a direction that inhibits tilt rotation of the camera unit 110. The torque of this rotational load in the energized state is adjustable, and details of the control will be described later.

[0021] In this embodiment, as shown in FIG. 4, the first electromagnetic brake 121 is disposed in a position facing the first motor 120 with the camera unit 110 interposed therebetween. This configuration prevents the center of gravity of the second rotating unit 111 from being biased relative to the second rotating shaft 140. This stabilizes rotation around the second rotating shaft 140 when installed for vertical shooting, making it less likely that the angle of view will shift. Note that the location of the first electromagnetic brake 121 is not limited to this, and it may be connected to the first rotating shaft 115A, which is in the same direction as the first motor 120 when viewed from the camera unit 110. In this case, twisting due to the rotational drive of the motor and the rotational load of the electromagnetic brake does not occur, enabling more accurate tilting.

[0022] Next, a pan rotation mechanism when the PTZ camera 100 of this embodiment is installed for vertical shooting will be described with reference to FIG.

[0023] 5 is a cross-sectional view of the second rotation axis 140 showing the pan rotation mechanism of the PTZ camera 100. As shown in Fig. 5, the pan base 116 has the second rotation axis 140. The pan base 116 is supported by the base unit 112 so as to be capable of pan rotation. As a result, the second rotation unit 111 is supported by the base unit 112 so as to be rotatable around the second rotation axis 140.

[0024] Here, the rotation of the pan base 116 in the pan direction is performed by a second motor 141 (pan motor) serving as an actuator. The second motor 141 is directly connected to the second rotating shaft 140, and can rotate the pan base 116 in the pan direction at a reduction ratio of 1:1. The second motor 141 is a DC brushless motor, and is driven for panning by a direct drive mechanism. The second motor 141 is used for panning in the normal position, and for tilting in the vertical shooting position.

[0025] A second electromagnetic brake 142 is connected to the second rotating shaft 140 and is disposed between the second motor 141 and the camera unit 110. The second electromagnetic brake 142 applies a rotational load to the second rotating shaft 140 in a direction to stop rotation. Like the first electromagnetic brake 121, the second electromagnetic brake 142 is a rotational load mechanism that is excited and activated when energized, thereby applying a rotational load as a frictional load in a direction that inhibits pan rotation of the pan base 116. The torque of this rotational load when energized is adjustable, and details of the control will be described later.

[0026] Next, FIG. 6 shows a functional block diagram illustrating the configuration of a PTZ camera 100 according to an embodiment of the present invention.

[0027] The system control unit 160 is configured with a CPU, an MPU, etc., and controls the entire PTZ camera 100. The system control unit 160 also includes an attitude determination unit 161, which determines, based on information acquired from the acceleration sensor 180, whether the installation attitude of the PTZ camera 100 is a normal attitude or an attitude rotated 90° for vertical shooting.

[0028] The storage unit 170 is configured with, for example, a RAM, a ROM, and a hard disk, and is mainly used as a storage area for programs executed by the system control unit 160 and various data.

[0029] The pan / tilt control unit 162 is controlled by the system control unit 160, and controls the rotation direction, rotation speed, voltage, etc. of the first motor 120 and the second motor 141, and also controls the voltage of the first electromagnetic brake 121 and the second electromagnetic brake 142. Details of this control will be described later.

[0030] The communication unit 190 communicates with an external device using a wired or wireless network or the like. The external device includes an input means such as a controller or a PC, and the user can operate the external device to configure the PTZ camera 1. The external device may be configured independently of the PTZ camera, or may be configured integrally with the PTZ camera.

[0031] Next, control of the PTZ camera 100 in the embodiment of the present invention will be described with reference to Figures 7 and 8. Figure 7 is a flow showing the flow when operating the PTZ camera 100 in the embodiment of the present invention. The processing of this flow is performed by the system control unit 160 of the PTZ camera 100. As an example, the following description will be given of a case where the user installs the camera for vertical shooting and drives the second motor 141 (pan motor). However, similar processing may be performed on the first electromagnetic brake 121 when the first motor 120 (tilt motor) is driven.

[0032] In addition, the second motor (pan motor) rotates the PTZ camera 100 in the vertical direction (tilt direction) when installed for vertical shooting. The first motor 120 (tilt motor) rotates the PTZ camera 100 in the horizontal direction (pan direction) when installed for vertical shooting. This flow is performed when the installation of the PTZ camera 100 is complete.

[0033] First, in step S100, system control unit 160 acquires information from acceleration sensor 180, and the process proceeds to step S110.

[0034] In step S110, the system control unit 160 determines whether the attitude of the PTZ camera 100 is the normal attitude or the vertical shooting installation (vertical shooting attitude) rotated 90° from the normal attitude based on the acquired information from the acceleration sensor 180. If it is determined to be the vertical shooting attitude, the process proceeds to step S120.

[0035] In step S120, the system control unit 160 determines whether or not a drive command in the vertical direction (tilt direction) has been received from the outside via the communication unit 190. If a drive command in the vertical direction (tilt direction) has been received, the process proceeds to step S130. In step S130, the pan / tilt control unit 162 controls the second motor 141 and the second electromagnetic brake 142 based on the first control protocol. Specifically, the pan / tilt control unit 162 controls the second electromagnetic brake 142 to apply a rotational load torque T2 to the second rotating shaft 140. The pan / tilt control unit 162 also controls the second motor 141 so that the rotational torque is T1. Note that the rotational torque T1 of the second motor 141 is greater than the rotational load torque T2 of the second electromagnetic brake 142.

[0036] On the other hand, if it is determined in step S120 that a drive command in the vertical direction (tilt direction) has not been issued, the pan / tilt control unit 162 controls the second electromagnetic brake 142 based on the second control protocol. Specifically, the pan / tilt control unit 162 controls the second electromagnetic brake 142 to apply a load of rotational load torque T3, which is greater than rotational load torque T2, to the second rotating shaft 140. The first control protocol and the second control protocol will be described in detail later.

[0037] On the other hand, if it is not determined in step S110 that the posture is for vertical shooting, the process proceeds to step S150.

[0038] In step S150, it is determined whether a drive command in the pan / tilt direction has been issued. If a drive command in the pan / tilt direction has been issued, the process proceeds to step S160. In step S160, the pan / tilt control unit 162 controls the first motor 120 or the second motor 141 based on the normal protocol.

[0039] Control based on the normal protocol is control of the first motor 120 or the second motor 141 based on a drive command in the pan / tilt direction, but control that does not control the first electromagnetic brake 121 or the second electromagnetic brake 142. If it is not determined that the posture is for vertical shooting, this is the originally intended installation method, and therefore it is determined that there is no need to use the first electromagnetic brake 121 or the second electromagnetic brake 142 when the actuator is rotating, and such control is performed.

[0040] If there is no drive command in the pan / tilt direction, the process proceeds to step S 170. In step S170, the pan / tilt control unit 162 controls the first electromagnetic brake 121 or the second electromagnetic brake 142 based on the second control protocol.

[0041] 8 is a conceptual diagram showing the relationship between the torque of the second motor 141 and the torque of the second electromagnetic brake 142 when the PTZ camera 100 according to the embodiment of the present invention is installed for vertical shooting. Hereinafter, as an example, a case where the user installs the camera for vertical shooting and drives the second motor 141 will be described, but the same applies when the first motor 120 is driven.

[0042] In Figures 8(a) to (c), the horizontal axis represents time t, and the vertical axis represents the drive torque of the second motor 141 in Figure 8(a), the rotational load torque of the second electromagnetic brake 142 on the second rotating shaft 140 in Figure 8(b), and the rotational speed of the camera unit 110 in Figure 8(c).

[0043] First, from time t1 to time t4 in FIGS. 8(a) to 8(c), the PTZ camera 100 receives an external drive command to perform a pan rotation. Therefore, the second motor 141 and the second electromagnetic brake 142 are controlled based on the first control protocol described above. As shown in FIG. 8(c), from time t1 to time t2, the second motor 141 is instructed to accelerate from a speed of 0 to a speed of v1. At this time, as shown in FIG. 8(a), the second motor 141 is controlled to decrease to a torque T1. Meanwhile, the rotational load torque of the second electromagnetic brake 142 is controlled to increase from 0 to a torque T2, as shown in FIG. 8(b). Here, the rotational torque T1 of the second motor 141 is greater than the rotational load torque T2 of the second electromagnetic brake 142.

[0044] Next, from time t2 to time t3 in Figures 8(a) to 8(c), the second motor 141 is instructed to rotate at a constant speed v1 shown in Figure 8(c). At this time, the second motor 141 is controlled at a constant torque T1 as shown in Figure 8(a). Furthermore, the second electromagnetic brake 142 is controlled at a constant torque T2 as shown in Figure 8(b). This allows the PTZ camera of this embodiment to increase the holding torque around the rotation axis during motor rotation. This makes it possible to prevent the angle of view from being displaced by disturbances such as vibrations on the installation surface.

[0045] Next, from time t3 to time t4 in FIGS. 8(a) to 8(c), the second motor 141 is instructed to decelerate from the speed v1 shown in FIG. 8(c) until it stops. At this time, the rotational load torque of the second electromagnetic brake 142 is controlled to increase from torque T2 to torque T3. As a result, the PTZ camera of this embodiment can increase the holding torque around the rotation axis during deceleration of the rotational movement compared to when operating at a constant speed. This makes it possible to prevent the angle of view from being displaced by the inertial force generated by deceleration of the rotational movement. Note that the second electromagnetic brake 142 in the first control protocol may not be energized, and the rotational load torque may be zero.

[0046] Next, after time t4 in Figures 8(a) and (b), no instruction to drive pan rotation is given to the PTZ camera 100. Therefore, as described above, the second electromagnetic brake 142 is controlled based on the second control protocol. At this time, as shown in Figure 8(b), the second electromagnetic brake 142 is controlled to apply a load of torque T3, which is greater than torque T2, to the second rotation shaft 140. This makes it possible to provide a holding torque around the second rotation shaft 140 even when rotation is stopped. This makes it possible to prevent the angle of view from shifting due to disturbances such as vibrations of the installation surface while rotation is stopped when the camera is installed for vertical shooting.

[0047] In this way, this embodiment can provide a pan head device that can suppress deviations in pan / tilt angles due to inertial forces and disturbances during rotation of the DC motor.

[0048] (Second embodiment) The second embodiment will be described below with reference to Fig. 9. The configuration of the PTZ camera 100 in this embodiment is the same as that in the first embodiment, and therefore description thereof will be omitted.

[0049] The PTZ camera 100 in the second embodiment allows the user to select between a normal shooting mode and a vertical shooting mode from an external device. The PTZ camera 100 controls the first electromagnetic brake 121 and the second electromagnetic brake 142 according to the shooting mode selected by the user. Therefore, the PTZ camera 100 in the second embodiment does not need to include the acceleration sensor 180 for detecting the installation attitude.

[0050] Next, control of the PTZ camera 100 in this embodiment will be described with reference to Fig. 9. Fig. 9 is a flow showing the flow when operating the PTZ camera 100 of the second embodiment. The processing of this flow is performed by the system control unit 160 of the PTZ camera 100. Hereinafter, as an example, a case will be described in which the user sets the camera for vertical shooting and drives the second motor 141, but similar processing is also performed when the first motor 120 is driven. This flow is performed when an instruction regarding the shooting mode is received from an external device.

[0051] First, in step S200, the system control unit 160 determines whether the selected shooting mode is the normal shooting mode or the vertical shooting mode based on a control instruction received from an external device. If it is the vertical shooting mode, the process proceeds to step S210. If a drive instruction in the vertical direction (tilt direction) is received in step S210, the pan / tilt control unit 162 controls the second motor 141 and the second electromagnetic brake 142 based on the first control protocol. On the other hand, if a drive instruction in the vertical direction (tilt direction) is not received in step S210, the pan / tilt control unit 162 controls the second electromagnetic brake 142 based on the second control protocol.

[0052] If it is determined in step S200 that the shooting mode is not the vertical shooting mode, the process proceeds to step S240. If a drive command in the pan / tilt direction has been issued in step S240, the process proceeds to step S250. In step S250, the pan / tilt control unit 162 controls the first motor 120 or the second motor 141 based on the normal protocol. Also, if it is determined in step S240 that a drive command in the pan / tilt direction has not been issued, the process proceeds to step S260. In step S260, the pan / tilt control unit 162 controls the first electromagnetic brake 121 or the second electromagnetic brake 142 based on the second control protocol.

[0053] In this way, in this embodiment, the user can select between normal shooting mode and vertical shooting mode from an external device. Also, in this embodiment, a camera platform device can be provided that can suppress deviations in pan / tilt angles due to inertial forces and disturbances during rotation of the DC motor.

[0054] (Third embodiment) The third embodiment will be described below with reference to Fig. 10. The configuration of the PTZ camera 100 in this embodiment is the same as that in the first embodiment, and therefore description thereof will be omitted.

[0055] The PTZ camera 100 in the third embodiment has a function of detecting an error in the pan / tilt rotation operation due to a collision of the camera unit 110 or the like, and stopping the rotation of the motor. For example, if the rotation operation of the second motor 141 stops due to an error, the second rotating unit 111 may not be held due to inertial force, and may collide with the end of rotation. At this time, it is conceivable that a collision sound or damage to parts may occur. Therefore, in this embodiment, control when the motor rotation stops due to an error or the like during pan / tilt rotation operation will be described.

[0056] 10 is a flow chart showing the procedure for operating the PTZ camera 100 according to the third embodiment. The processing of this flow chart is performed by the system control unit 160 of the PTZ camera 100. Hereinafter, as an example, a case will be described in which the user sets up the camera for vertical shooting and drives the second motor 141, but similar processing is also performed when the first motor 120 is driven. This flow chart is performed when the installation of the PTZ camera 100 is complete.

[0057] 10, PTZ camera 100 installed for vertical shooting first performs the processes of steps S300 to S330, as in the first embodiment, and second motor 141 and second electromagnetic brake 142 are controlled based on the first control protocol. After step S330, the process proceeds to step S350. If a motor stop due to an error during pan / tilt drive is detected in step S350, the process proceeds to step S360.

[0058] In step S360, the second electromagnetic brake 142 is controlled based on the second control protocol, and a rotational load of torque T3 in FIG. 8 is applied to the second rotation shaft 140. In the third embodiment, torque T3 is the maximum torque of the second electromagnetic brake 142. On the other hand, if in step S310 the installation attitude is not an attitude for vertical shooting, the process proceeds to step S370. If in step S370 a drive command in the pan / tilt direction has been issued, the process proceeds to step S380. In step S380, the pan / tilt control unit 162 controls the first motor 120 or the second motor 141 based on the normal protocol.

[0059] If there is no drive command in the pan / tilt direction in step S370, the process proceeds to step S390. In step S390, the pan / tilt control unit 162 controls the first electromagnetic brake 121 or the second electromagnetic brake 142 based on the second control protocol.

[0060] As described above, this embodiment provides a pan / tilt head device that can suppress deviations in pan / tilt angles due to inertial forces and disturbances during rotation of the DC motor. Furthermore, if motor operation stops due to an error, the electromagnetic brake is controlled with a torque greater than that during rotation. This prevents the rotating part from colliding with the end of rotation due to inertial forces being unable to be held in place when the motor stops during rotation.

[0061] The present invention has been described in detail above based on its preferred embodiments, but the present invention is not limited to these specific embodiments, and various modifications and changes can be made in various forms without departing from the spirit of the present invention. [Explanation of symbols]

[0062] 100 PTZ cameras 100a pan head device 110 Camera Department 111 Second rotating part 112 Base 113 Lens 114 Telescope tube support member 115 First Rotation Axis 116 Pan Base 117 Bearing member 117 120 First Motor 121 First electromagnetic brake 140 Second Rotation Axis 141 Second Motor 142 Second electromagnetic brake 150 Imaging unit 151 Imaging processing unit 152 Lens control unit 160 System control section 161 Posture determination section 162 Pan / tilt control unit 170 Storage section 180 Accelerometer 190 Communications Department 300 tripod

Claims

1. A camera platform device to which a camera unit can be attached, a direct drive mechanism including an actuator that rotates the camera unit; a load means for applying a rotation load to the rotation axis of the camera unit in a direction to stop the rotation, The camera platform device is characterized in that the load means applies the rotational load to the rotation shaft while the actuator is being driven.

2. a setting means for setting the torque of the rotational load and the rotational torque of the actuator; 2. The camera head device according to claim 1, wherein the setting means sets the rotation load torque to be smaller than the rotation torque of the actuator while the actuator is being driven.

3. 3. The camera head device according to claim 2, wherein the setting means sets the rotation load torque to a maximum torque when the actuator is not being driven.

4. further comprising a determination means for determining the orientation of the camera unit; 2. The camera head device according to claim 1, wherein when the determining means determines that the camera is oriented for portrait photography, the load means applies the rotational load to the rotation axis while driving the actuator.

5. 5. The camera platform device according to claim 4, wherein the determining means determines the orientation of the camera unit based on an output from an acceleration sensor.

6. 5. The camera platform device according to claim 4, wherein the determining means determines the orientation of the camera unit based on an input from a user.

7. a detection means for detecting an error in the rotational operation of the camera unit, and a setting means for setting the torque of the rotation load, 2. The camera platform device according to claim 1, wherein when the detection means detects a stop due to an error during driving of the actuator, the setting means changes the torque of the rotation load.

8. 2. The camera platform device according to claim 1, wherein the load means is an electromagnetic brake.

Images