Patent Application
20150071627
When shooting videos using an imaging device such as a camera phone or a light camcorder, hand and body movements tend to transmit to the camera thus producing shaky videos. There are imaging devices with features such as built-in image stabilization to improve the video quality, and these features utilize either a software image stabilization technique to smooth minor jitters in the video or an optical stabilization technique where a lens is physically shifted inside the camera to counter the movements of the camera body. In general, these techniques work well for small vibrations measured within a few degrees of movement, however, larger rotating movements of the camera associated with walking or running requires other external devices to stabilize the camera.
For many years, a device such as a steadycam uses a counterweight to balance the camera such that the camera and the counterweigh pivot about a swivel joint located somewhere in between. As the operator's hand rocks back and forth during operation, the camera remains leveled due to the counterweight and the resulting video image is generally steady.
There are a few disadvantages to this design. The camera has to be balanced with the counterweight to remain leveled and once it is in a balanced position, it cannot be pitched up or down and still remain stabilized. The device is bulky and general difficult to operate due to the inherent lack of controls in pitching or panning motion.
In the past few years, motorized camera stabilizer commonly called brushless gimbals have been introduced that solve many of the problems associated with the mechanical, counterweight stabilizers. Generally, brushless gimbals utilize motors to drive the camera about the pitch, roll, and yaw axis and allow the user to pitch the camera up and down smoothly by pressing a corresponding button.
While brushless gimbals are relatively easy to use when paired with a predefined camera, however the low torque, brushless motors require calibration when used with cameras of slightly difference in weight. Also, a unique mounting bracket is needed for cameras of different geometries such that the center of gravity of the camera has to be in line with the center axis of motor rotation at all times. This makes the brushless gimbal not conveniently adaptable to different camera types, and therefore most manufacturers simply make a unique brushless gimbal for one or two of the most popular camera models. Lastly, the configuration of the brushless motors relative to the camera prevents the operator to view the camera screen during operation.
It is the object of the present invention to provide an automatic stabilizer apparatus using a differential gear configuration that is compact, lightweight, attractive, simple to use, inexpensive to manufacture, and versatile in adapting to multiple types of imaging devices.
The apparatus includes: a first and second drive assembly that are positioned opposite and collinear to each other and attached to the electrical compartment, a differential gear assembly containing three miter gears housed in a configuration such that two opposing drive gears mesh with the third gear being the driven gear, and each drive gear is attached to the output shaft of the drive assembly, a camera bracket, having a thumb screw to secure an imaging device, attached to one end of the driven gear such that the driven gear and the camera bracket rotates in unison, an electronic housing having orientation sensors, main processor unit, power management and drive circuit, and a removable handle, attached to the underside of the electronic housing, having batteries to power the device.
When both drive gears rotate in the opposite direction, and at the same speed, the camera pitches about the axis along the centerline of the drive gears, and when the drive gears rotate in the same direction, and at the same speed, the camera rolls about the axis along the centerline of the driven gear. Varied speed and direction of the two drive motors enable the camera to rotate in any combinations of motions about the two axes.
In my present application I have developed and applied the benefit of the differential drive system to an automatic stabilizer apparatus to provide stabilization of the camera in the pitch and roll axis while maintaining a small footprint and allowing the operator to have full view of the camera display screen.
These, as well as other features of the present invention, will become more apparent upon reference to the drawings wherein:
c is a perspective view of a portable battery pack;
b is a perspective view of a 12V vehicle power adapter;
c is a perspective view of a removable handle with battery cells;
a is a perspective view of the automated stabilizer apparatus with reference coordinate frames;
b is a side view of the automated stabilizer apparatus with reference coordinate frames;
c is a front view of the automated stabilizer apparatus with reference coordinate frames.
While the invention is described in conjunction with the accompanying drawings, the drawings are for purposes of illustrating exemplary embodiments of the invention and are not to be construed as limiting the invention to such embodiments. It is understood that the invention may take form in various components and arrangement of components beyond those provided in the drawings and associated description. Within the drawings, like reference numerals denote like elements. The term “device” is frequently used in describing an imaging object mounted to the apparatus which means a camera, video recorder, camera phone, laser, lens, and sensors.
The automatic stabilization apparatus is comprised of several subassemblies, which combined to provide device control while giving special consideration to the physical size, visual obtrusiveness, adaptability to different devices, and cost of manufacturability. In other words, an automatic stabilization apparatus is small, light, attractive, and inexpensive.
It is worth to mention that although
Referring to
The enclosure 14, is injection molded or machined, having means to mates to the drive housing 9 to add rigidity to the drive system and to prevent dirt from contaminating the spur gears. The drive housing 9 is a central structural component of the drive system because it provides rigidity for the drive train and contains location holes for gear shafts and ball bearings 11. It is this component that allows the spur gears to rotate smoothly without rub or play during operation. In the preferred embodiment, the housing 9 is made from high strength engineer plastic through injection molding using manufacturing technics required to hold very tight tolerances. In some other embodiment, the housing 9 is fabricated from metal such as aluminum where tight tolerances can be easily achieved.
Referring to
In some other embodiment feedback signal, illustrated in
In yet another embodiment, illustrated in
In
This invention does not restrict the device to be positioned on top of the apparatus. In some other embodiments, the device is positioned in front of the apparatus or below the apparatus by using different device mounting brackets.
In some other embodiment, the bottom shell 52 of the main structure 50 and the motor housings 9 (
There are two circuit boards 53 & 56 housed inside the main structure; sensors and control components are located on the first board 53, and power distribution components are located on the second board 56. An opening on each side of the structure 50 enables power and signal wires to be routed from the circuit boards 53 & 56 to the motors and rotary encoders in the drive systems.
A microcontroller, resides on the first circuit board 53, performs continuous system control loops including updating sensor signals to determine the current physical orientation of the apparatus, processing controls algorithm to determine a trajectory path for the motors, and finally send commands to drive the motors. Also located on the first circuit board 53 are chip based sensors capable of measuring orientation of the apparatus at a very high rate of speed such that fresh orientation data are communicated to the microcontroller upon request. Finally, sharing the same circuit board 53 are the motor driver chips that convert signals from the microcontroller into speed and direction commands to the drive motors.
An ON-OFF switch 57, control button 55, and power socket 54 located around the sides of the apparatus provide means for the operator to interface with the apparatus. A socket, terminal strip or connector may be positioned such that the socket 54 is exposed for quick and error-proof connection of the power adaptor. The socket 54 is preferably attached firmly to the second circuit board 56 by soldering to eliminate the needs for power wires from the socket 54 to the circuit board 56. Control buttons 55, may be multi-position slide switch, momentary contact switch, or permanent contact switch, are used to select different modes of operation preprogrammed into the microcontroller.
It is worth to mention that although
As shown in
Turning to
Referring to
Main Electronic Components and their Functions
The microcontroller is a main processor that coordinates and controls all major activities in the system. The sequence of operation, written in program codes and resides in the memory within the microcontroller, is performed in a perpetual programming loop at a high rate of speed.
When magnetic encoders are used for feedback, the magnetic encoder chips communicate the current angle positions of the drive shafts to the microcontroller. These values are then converted to orientation angles of the device relative to a fixed frame by the microcontroller.
In applications where the device coordinates (Xd, Yd, Zd) need to be stabilized with respect to the fixed coordinates (Xf, Yf, Zf), the sensor measures its absolute orientation (Xs, Ys, Zs) relative to the fixed coordinates and feeds this data to the microcontroller. The device coordinates are usually not equal to fixed coordinates while the apparatus is in motion; this is because the sensor measures current rotation of the apparatus and the device is at the position based on previous loop command. Adjustments are always made by the microcontroller to minimize the error between the device coordinate and the fixed coordinate.
b illustrates an instant when the device needs to tilt (rotate about the Xd axis) to maintain leveled with respect to the fixed axis. While the sensor reads the absolute tilt angle s of the apparatus, the encoders provides the tilt angle d1 of the device relative to the sensor. The motors have to rotate the device an angle equivalent to d2, which is s minus d1. In the differential drive configuration, the microcontroller commands the motors to rotate in the opposite directions and at the same speed to achieve tilting motion.
c shows an example where the device needs to roll about the Zd axis to maintain leveled. The sensor reads the angle t, which is Xs relative to Xf, and the encoder provides roll angle a2, which is Xd relative to Xs. Thus, the motors must rotate the device an angle equivalent to a1 (t minus a2). The microcontroller commands the motors to rotate in the same direction and at the same speed to roll about the Zd axis. Varied speed and direction of the two drive motors enable the driven gear the device to rotate in any combinations of motions about the two axes.
In every process loop, the microcontroller communicates with the sensors through a high speed serial bus such as serial peripheral interface (SPI) to acquire current orientation data of the sensors relative to a fixed frame. In the preferred embodiment, the sensor is a microelectralmechanical (MEMS) inertial measurement unit (IMU) having a rate gyro, accelerometer, magnetometer (or compass), and a central processing engine built into one chip. Due to recent advanced in MEMS manufacturing techniques, this type of sensor has only been available for mass distribution in recent years. Sensors such as a MPU-6000 produced by Invensense and BMX055 by Bosch Sensortec enables a single chip to accommodate a footprint of approximately 4×4 mm on the circuit board whereas three components were needed in the past.
Another major advantage of having three sensors built into one chip is that the misalignments between sensors axes are dramatically reduced. For example, when individual chips such as rate gyro and an accelerometer are soldered separately on a circuit board, tolerances inherent in the handling process will cause the axes to not be parallel. Therefore, every board is unique and complicated calibration procedure is required to accommodate for axes misalignment. For the single chip sensor, misalignment is at a micron scale in the MEMS manufacturing processes and is negligible in most applications.
Furthermore, the benefit of having a processing engine on board the chip to perform complicated algorithms is to free up the microcontroller to complete other tasks. Typically, the accelerometer and rate gyro send out raw data, or unfiltered data, to the microcontroller for processing. Signals from the accelerometer are inherently unstable due to external vibration or electrical noise; likewise the measurements from the rate gyro are not entirely useful due to accumulating drift over time, which is typical of any MEMS rate gyro. Companies such as Invensense and Bosch Sensortec have developed their own algorithms to combine the features of both sensors while discriminate noise and unwanted vibration to produce smooth and accurate output signals. With the processor engine built in the sensor chip, the time consuming algorithm calculations are performed entirely inside the sensor chip and not the microcontroller. The result is an inexpensive and reliable sensor that measures absolute orientation of the base of the apparatus relative to a fixed frame.
Finally, the motor drivers are the last major control components on the circuit board. In this embodiment, the drive source consists of two bidirectional DC motors. In some other embodiments, stepper motors, brushless motors, or gear motors are used such that sufficient torque is generated by the motors to move the device expeditiously. For bidirectional DC motors, the driver typically consists of an H-bridge electronic circuit built into a chip that enables a voltage be applied across a motor in either direction. Pulsing this voltage effectively permits the motor to run at different speeds in either direction. The driver communicates with the microcontroller through a plurality of digital pins such that a low voltage pulse train from the microcontroller is received by the driver which then produces higher voltage required to drive the motors. Longer pulses or duty cycle correspond to higher output torque and faster motor speed.
In every processing loop, the microcontroller retrieves the latest signals from the two encoders to establish the most current position of the drive shafts. The drive motors are then commanded to rotate at speeds according to how far the device is from a desired position as calculated by the microcontroller. The farther the device is from a desired position, the faster the motors must move to compensate for the difference. A proportional-Integral-Differential (PID) control system is implemented by the microcontroller to control the motor most expediently as well as produce minimal system instability.
| Number | Date | Country | |
|---|---|---|---|
| 61877163 | Sep 2013 | US |
