The present invention generally pertains to pan and tilt systems. More specifically, the present invention pertains to camera pan and tilt systems that utilize hobby servo motors.
Cameras commonly include a limited field of view. In many situations, it is desirable to change the positioning of a camera to capture multiple fields of view. For example, in a store setting, it may be desirable to have a camera that can view both an entry way and a cash register area. Pan and tilt systems are used to control the positioning of a camera, and thus enable the camera to capture multiple fields of view.
A hobby servo motor (a.k.a. simply a “servo”) is a device having a rotatable output shaft. The output shaft can typically be positioned to specific angular positions in accordance with a coded input signal received by the servo. It is common that a particular angular position of the output shaft will be maintained as long as a corresponding coded signal exists on an input line. If the coded signal changes, the angular position of the shaft will change accordingly. Control circuits and an internal potentiometer are typically included within the servo motor casing or housing, and are functionally connected to the output shaft. Through the potentiometer (e.g., a variable resistor), the control circuitry is able to monitor the angle of the output shaft. If the shaft is at the correct angle, the motor actuates no further changes. If the shaft is not at the correct angle, the motor is actuated in an appropriate direction until the angle is correct.
There are different types of servo motors that include output shafts having varying rotational and torque capabilities. For example, the rotational and/or torque capability of an industrial servo is typically less restricted than that of a hobby servo. That being said, hobby servos are generally commercially available at a cost that is much less than that associated with industrial servos.
Because hobby servos are relatively small and inexpensive, they are popular within the hobby-mechanical industry for applications such as, but by no means limited to, hobby robotic applications and radio-controlled models (e.g. cars, planes, and boats). One example of a hobby servo is the Futaba S-148 available from Futaba Corporation of America located in Schaumburg, Ill.
The output shaft of a hobby servo is typically capable of traveling approximately 180° (possibly up to 210° or more depending on manufacturer). Rotation of the hobby servo shaft is limited typically by one or more internal mechanical stops. It is also typically true that the output shaft of a hobby servo is capable of producing a relatively limited amount of torque power. The torque and rotational limitations of a hobby servo are adequate for many hobby applications, such as model car steering control, puppet control, robot arm or head movement and/or model airplane rudder control.
Some hobby servos can be mechanically altered to provide an extended range of rotation. However, this solution requires mechanical alteration that often only works for some types of servos. Rotational control for most hobby servos is limited by the internal potentiometer being utilized to monitor rotation. When a hobby servo is hacked or modified to extend the rotational capacity, the internal potentiometer of the servo will, in most instances, not be configured to monitor angular positions too far beyond the original range of rotation. Thus, the control system of a hacked servo will commonly not be configured to accurately position the servo output shaft too far within the extended range of rotation.
Pan and tilt systems are provided. Pan and tilt systems illustratively include a pan hobby servo motor having a splined output shaft. The splined output shaft rotates about an axis of rotation. In an embodiment, an angular position of the splined output shaft is controlled based at least in part on a coded input signal and an external potentiometer. A pan auxiliary gear is illustratively rotatably coupled to the hobby servo motor splined output shaft. The pan auxiliary gear has an axis of rotation that is approximately parallel to the splined output shaft axis of rotation. In an embodiment, a tilt system is functionally engaged to the pan auxiliary gear such that rotation of the pan auxiliary gear is translated to the tilt system.
I. Overview of Pan and Tilt System
System 100 includes a tilt system 200 and a pan system 250. Tilt system 200 includes a tilt axis of rotation 201. As will be described later in greater detail, tilt system 200 includes components that are able to rotate an attached camera about axis 201 in the direction shown by arrow 202 and in the direction opposite of that shown by arrow 202. Pan system 250 includes a pan axis of rotation 251. Pan system 250 includes components that are able to rotate an attached camera about axis 251 in the direction shown by arrow 252 and in the direction opposite of that shown by arrow 252.
II. Hobby Servo Motors
Servo 400 includes attachment flanges 404. Flanges 404 optionally include apertures such as apertures 405 formed therein for receiving an attachment mechanism (e.g., a screw, bolt, etc). The attachment mechanism is utilized to secure servo 400 within an operative environment. Servo 400 also includes an electrical connection 406 that enables the servo to receive electrical power and/or control signals.
Servo 400 includes a rotatable output shaft 402 also known as a servo spline or a servo splined output shaft. Shaft 402 optionally has an outer perimeter or periphery that has splines or teeth. It is common for shaft 402 to have a 23, 24 or 25 tooth configuration. The servo output shaft 402 is positioned to specific angular positions in accordance with a coded input signal received by the servo. It is common that a particular angular position will be maintained as long as a corresponding coded signal exists on an input line. If the coded signal changes, the angular position of the servo output shaft 402 will change accordingly.
In an embodiment, output shaft 402 includes a threaded orifice 422. Threaded orifice 422 extends into splined output shaft 402 from its distal end. As will be described later, orifice 422 is illustratively used to secure an item such as a gear to shaft 402. Servo 400 further includes a planar or relatively planar surface 421 that surrounds shaft 402. In accordance with one aspect of the present disclosure, gears that are attached to, rotatably coupled to, or functionally engaged to shaft 402 also include a planar or relatively planar surface. In such an embodiment, the gear surface and surface 421 are engaged to one another in a relatively flush relationship.
Rotation of a servo output shaft such as shaft 402 is typically limited to around 180°. In most cases, rotation is limited at least because of an internal mechanical stop. It is also common that servo output shaft 402 is capable of producing a relatively limited amount of torque power. The torque and rotational limitations of a hobby servo are adequate for many applications; however, some applications require a servo having torque power and/or a rotational capacity that is beyond the capability of a typical hobby servo. Increased torque power and/or rotational capacity enable greater mechanical flexibility.
In accordance with one embodiment of the present disclosure, hobby servo motors such as servo 400 are internally modified to enable a range of output shaft rotation that is greater than its “off-the-shelf” capability. For example, in accordance with one embodiment, an internal mechanical stopping mechanism, which prevents rotation past a predetermined angle, is removed from hobby servo motor to enable for continuous rotation in either direction. As a result of the modification, the rotatable output shaft of a hacked or modified servo is able to rotate beyond the range of rotation prior to the modification.
Following modification of servo 400, limitations inherent to the internal potentiometer make it a poor choice for subsequent control functionality. As previously mentioned, in a normal servo operating configuration, the servo motor rotates the servo output shaft corresponding to the coded signal received by the servo. The output shaft is rotated until the signal from the internal potentiometer of the servo, which corresponds to the angular position of the servo output shaft, matches the coded signal received by the servo. Most hobby servos contain internal potentiometers such as potentiometer 452 shown in
In accordance with one aspect of the present disclosure, the internal potentiometer is disconnected and an external/auxiliary potentiometer is inserted into the control scheme to facilitate proportional control of the servo splined output shaft. In an embodiment, servo 400 utilizes the coded input signal and the signal from an external potentiometer to rotate and position the output shaft. A particular external potentiometer having any of a variety of control characteristics can be selected and implemented based on the requirements of a given application. Therefore, a potentiometer with a rotational range of substantially less than or greater than 180° can be selected and implemented as desired.
A more detailed description of modifying a hobby servo is described in the U.S. patent application having the Ser. No. 11/153,800, which was previously incorporated by reference in its entirety.
III. Tilt Systems
Outer mounting bar 500 includes a left bar 501, a bottom/center bar 502, and a right bar 503. Inner mounting bar 550 includes a left bar 551, a bottom/center bar 552, and a right bar 553.
Tilt servo motor 210 illustratively includes a tilt servo gear 521 functionally engaged to its rotatable splined output shaft such as shaft 402 shown in
Inner mounting bar 550 illustratively includes an auxiliary tilt gear 522. Auxiliary gear 522 and bar 550 are illustratively attached or connected in a fixed position such that the relative positioning of gear 522 to bar 550 does not change.
In an assembled tilt system, tilt servo gear 521 and auxiliary gear 522 are functionally or rotatably coupled or engaged such that rotation of gear 521 is translated to gear 522. In an embodiment, such as that shown in
System 200 optionally includes an external potentiometer 530 and an auxiliary rotatable shaft 531. Auxiliary shaft 531 is illustratively rotatably coupled to external potentiometer 530 such that rotation of auxiliary shaft 531 is directly translated to external potentiometer 530. Auxiliary shaft 531 is also illustratively functionally engaged or coupled to auxiliary gear 522 through an aperture 532. Thus, rotation from gear 522 is directly translated to shaft 531 and to potentiometer 530 (i.e. the angular position or motion of gear 522 directly corresponds to the position or motion of shaft 531). In an embodiment, auxiliary shaft 531 is parallel or approximately parallel to the splined output shaft of the tilt hobby servo motor.
As was previously described, hobby servo motors commonly include an internal potentiometer and a mechanical stop or stops that limit the rotational capability or capacity of the hobby servo motors (e.g. limited to rotation of less than one hundred and eighty degrees). In an embodiment, tilt servo 210 initially included an internal potentiometer and a mechanical stop, but they are removed from servo 210 in tilt system 200 to enhance or increase the rotational capacity of the servo. In an embodiment, the angular position of the splined output shaft of servo 210 is controlled based at least in part upon external potentiometer 530. For example, the angular position is based upon an output signal generated by potentiometer 530. The output signal illustratively corresponds to and is generated based upon the rotation and/or angular position of auxiliary shaft 531 and/or auxiliary gear 522. In an embodiment, the angular position of the splined output shaft is also based upon a coded input signal. As was previously described, the use of an external potentiometer allows for proportional control of the angular position of the servo output shaft over a greater range than would be possible by only using an internal potentiometer commonly included in hobby servo motors.
It should be noted that the combination of an auxiliary gear such as gear 522 and an external potentiometer such as potentiometer 530 provides advantages over other pan and tilt systems such as systems that directly use an output shaft of a hobby servo to position a camera. By indirectly rotating the tilt system (i.e. the tilt axis of rotation 201 shown in
Outer mounting bar 500 includes a servo aperture 541 and an auxiliary aperture 542. Apertures 541 and 542 create frames or supports that hold servo 210 and potentiometer 530 in place. An illustrative example of servo 210 and potentiometer 530 mounted within the apertures is shown in
It is worth noting that although tilt systems such as tilt system 200 are shown in the context of operating in connection with a pan system such as pan system 250 in
IV. Pan Systems
Pan system 250 includes a pan servo 260. Servo 260 illustratively includes a pan servo gear 703. Gear 703 includes a female spline receiver such that it rotatably engages the splined output shaft of servo 260. The bottom surface of gear 703 is optionally planar or relatively planar and flushly engages a planar or relatively planar surface such as surface 421 in
Pan system 250 also illustratively includes apertures 710 that are used in securing a tilt system such as tilt system 200 shown in
Pan servo 260 has an axis of rotation 701 and rotates gear 703 about axis 701 in the direction shown by arrow 702 or in the opposite direction. Pan gear 703 is illustratively rotatably engaged with or coupled to auxiliary pan gear 708, and rotation from gear 703 is translated to auxiliary pan gear 708. Gear 708 is rotated about axis 251 in the direction shown by arrow 252 or in the opposite direction. It is worth noting that pan system 250 does not rotate an attached mechanical load such as a tilt system about servo 260's axis of rotation 701. Instead, pan system rotates a mechanical load about an axis that is parallel or approximately parallel to axis 701 and that is displaced from axis 701. Thus, servo 260 indirectly rotates an attached mechanical load.
In an embodiment, such as that shown in
As was previously described, hobby servo motors commonly include an internal potentiometer and mechanical stop that limit the rotational capability of the hobby servo motors (e.g. limited to rotation of less than one hundred and eighty degrees). In an embodiment, pan servo 260 initially included an internal potentiometer and a mechanical stop, but they are removed from servo 260 in tilt system 250 to enhance or increase the rotational capacity of the servo. In an embodiment, the angular position of the splined output shaft of servo 260 is controlled based at least in part upon external potentiometer 802. For example, the angular position is based upon an output signal generated by potentiometer 802. The output signal illustratively corresponds to and is generated based upon the rotation and/or angular position of auxiliary shaft 804 and/or auxiliary gear 708. In an embodiment, the angular position of the splined output shaft is also based upon a coded input signal. As was previously described, the use of an external potentiometer allows for proportional control of the angular position of the servo output shaft over a greater range than would be possible by only using an internal potentiometer commonly included in hobby servo motors.
It should be noted that the combination of an auxiliary pan gear 708 and an external potentiometer provide advantages over other pan systems such as systems that directly use an output shaft of a hobby servo to position a camera. By indirectly rotating the pan system (i.e. the pan axis of rotation 251 shown in
Embodiments of pan housing 705 include all dimensions and components within housing 705 are spaced or configured differently. It is worthwhile however to note specific dimensions of at least some embodiments. In one embodiment, length 1011 is 4 inches, width 1012 is 3 inches, height 1021 is 2 and 7/32 inches, distance 1022 is 25/32 of an inch, width 1014 is 21/32 of an inch, and width 1013 is 1 and 11/16 inches. In another embodiment, length 1011 is between 2 and 6 inches, width 1012 is between 1 and 5 inches, height 1021 is between 1 and 4 inches, distance 1022 is between one quarter of an inch to 2 inches, width 1014 is between one quarter of an inch to 2 inches, and with 1013 is between one quarter of an inch to 2 and one half inches.
In another embodiment, the ratios of the relative dimensions of the components within frame 705 are utilized in sizing the components. For example, any one dimension is illustratively any dimension so long as the relative dimensions or sizing of the other components within frame 705 are maintained. In this embodiment, a frame such as frame 705 can be made of any size and still maintain favorable mechanical load bearing capability and stability. In an embodiment, the ratio of the overall height 1021 to the overall length 1011 is between 45-65%. The ratio of the overall width 1012 to the overall length 1011 is 65-85%. The ratio of the distance from the top panel to the center panel 1022 to the overall height 1021 is 25-45%. The ratio of the width of each flange 1014 to the overall width 1012 is 15-25%. The ratio of the width of top panel and the center panel 1013 to the overall width is 75-85%, and the ratio of the width of top and center panel 1013 to overall length 1011 is 30-50%.
Embodiments of frame 705 are made from any type of material. In one embodiment frame 705 is made from a metal such as, but not limited to, aluminum, stainless steel, copper, or titanium. In one embodiment, frame 705 is made from 6061-T6 anodized aluminum. Embodiments also include any thickness of the individual components. In one embodiment, the thickness of frame 705 is between 1/32 of an inch to one half of an inch. Other components of pan and tilt system 100 shown in
In an embodiment, frame 705 is one piece. In such an embodiment, frame 705 is illustratively made by an extrusion process and apertures are mechanically stamped out. In another embodiment of a one piece frame, a casting process is used in which liquid metal is poured into a mold of the desired shape. Any other method of forming frame 705 as one piece is also within the scope of the present disclosure. Alternatively, frame 705 is made from multiple pieces and are attached together for example, but not limited to welding.
Pan system 1100 is illustratively used in a pan and tilt system such as pan and tilt system 100 in
V. Conclusion
Although the present disclosure has been described with reference to certain embodiments of tilt systems and pan systems, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
The present application is a continuation-in-part of, and is based on, and claims the benefit of U.S. utility patent application Ser. No. 11/153,800, filed on Jun. 15, 2005, and U.S. utility patent application Ser. No. 12/368,536, filed on Feb. 10, 2009, the contents of which are hereby incorporated by reference in their entireties, the former application being based on U.S. provisional application 60/584,288, filed on Jun. 30, 2004.
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Child | 11153800 | US |