A multi-modal vehicle includes a frame, a rotor pivotally mounted to the frame, the rotor including a first position and a second position circumferentially spaced from the first position, and a motor coupled to the rotor and configured to rotate the rotor, wherein, when the rotor is disposed in the first position, the rotor is configured to generate lift when actuated by the motor, wherein, when the rotor is disposed in the second position, the rotor is configured to engage a surface to transport the vehicle when actuated by the motor.

Not applicable.

BACKGROUND

During the last few decades there has been increased interest in the use of unmanned aerial and ground vehicles or robots for both military and civilian applications. Today, one of the most predominant forms of aerial robot is a quad-copter or a multi-copter, while for ground mobility many conventional robots rely on wheels. In practical applications, there could be many scenarios where a ground robot needs to negotiate large obstacles (larger than the wheel diameter) or even climb stairs. Similarly, for a flying robot there could be instances where terrestrial locomotion capability is highly desired for stealth purposes or for conserving energy to significantly increase mission endurance given that ground locomotion requires only a fraction of the power needed for flying. Current approaches for developing a hybrid aerial-terrestrial platform involve combining a flying vehicle with a ground robot, while using independent power actuators (motors) and propulsion systems (rotors, legs, wheels, etc.) for each mode of locomotion. For example, one could add wheels or legs to a quad-copter and have a separate set of motors for driving the wheels or legs. Another design involves using flapping wings for aerial locomotion and actuated legs for moving on the ground. Even though these approaches are feasible, they would result in highly non-optimal designs, mainly because of the additional weight and complexity of the redundant actuation systems. This also implies that such designs would not scale up with size easily. Some of the other designs use unpowered wheels and the vectored thrust from the four propellers to move the vehicle forward/backward on the ground and also for control. However, such an idea of indirect propulsion may require significantly more power, wasting the stored battery power and also lack the control authority during ground locomotion since the wheels are not powered. Another design uses a fixed-wing design and with actuated wings to crawl on the ground. However, for such designs the vehicle cannot take-off and land vertically and also crawling with wings is not an effective mode of terrestrial locomotion.

BRIEF SUMMARY OF THE DISCLOSURE

A multi-modal vehicle, comprising a frame, a rotor pivotally mounted to the frame, the rotor comprising a first position and a second position circumferentially spaced from the first position, and a motor coupled to the rotor and configured to rotate the rotor, wherein, when the rotor is disposed in the first position, the rotor is configured to generate lift when actuated by the motor, wherein, when the rotor is disposed in the second position, the rotor is configured to engage a surface to transport the vehicle when actuated by the motor. In some embodiments, the vehicle further comprises a tilting system configured to actuate the rotor between the first and second positions, the tilting system comprising an actuator. In some embodiments, the actuator comprises a servo actuator. In certain embodiments, the vehicle further comprises a control system configured to control the motor and the actuator using an algorithm. In certain embodiments, the algorithm comprises a proportional-derivative feedback controller. In some embodiments, the vehicle further comprises a shaft coupled to the motor, wherein the shaft is rotatable relative to the frame. In some embodiments, the vehicle further comprises a magnetic locking mechanism configured to lock the rotor in either the first position or the second position, wherein the second position of the rotor is circumferentially spaced 90 degrees from the first position. In certain embodiments, the locking mechanism comprises a first magnet mounted on the shaft, a second magnet mounted on the shaft, wherein the second magnet is circumferentially spaced from the first magnet, and a third magnet mounted on the frame. In certain embodiments, the first magnet is aligned with the third magnet when the rotor is in the first position and circumferentially spaced from the third magnet when the rotor is in the second position, and the second magnet is aligned with the third magnet when the rotor is in the second position and circumferentially spaced from the third magnet when the rotor is in the first position.

An embodiment of a multi-modal vehicle comprises a frame, a rotor pivotally mounted to the frame, the rotor comprising a first position and a second position circumferentially spaced from the first position about a first axis, and a motor coupled to the rotor and configured to rotate the rotor about a second axis that is different from the first axis, wherein, when the rotor is disposed in the first position, the vehicle is disposed in an aerial mode, wherein, when the rotor is disposed in the second position, the vehicle is disposed in a ground mode. In some embodiments, the rotor comprises at least one of carbon fiber prepreg, metal, and plastic. In some embodiments, the rotor comprises a plurality of circumferentially spaced blades and a cover extending about the blades. In certain embodiments, the rim comprises a rim configured to provide traction to the vehicle when the vehicle is in the ground mode to transport the vehicle along a surface, and the blades are configured to generate lift when the vehicle is in the aerial mode. In some embodiments, relative rotation is permitted between the cover and the blades of the rotor. In some embodiments, the vehicle further comprises a shaft coupled to the motor, wherein the shaft is rotatable about the first axis. In certain embodiments, the vehicle further comprises a magnetic locking mechanism configured to lock the rotor in either the first position or the second position, wherein the locking mechanism comprises a first magnet mounted on the shaft, a second magnet mounted on the shaft, wherein the second magnet is circumferentially spaced from the first magnet, and a third magnet mounted on the frame. In certain embodiments, the vehicle further comprises further comprising a tilting system configured to actuate the rotor between the first and second positions. In some embodiments, the tilting system comprises an actuator coupled to the frame, and an actuator arm coupled between the shaft and the actuator, wherein, in response to actuation of the actuator, the actuator arm is configured to rotate the shaft and the motor. In some embodiments, the vehicle further comprises a control system including a microcontroller, an inertial measurement unit, a motor controller, and a wireless transceiver. In certain embodiments, the rotor is configured to generate lift in response to actuation of the motor when the rotor is disposed in the first position, and the rotor is configured to engage a surface to transport the vehicle in response to actuation by the motor when the rotor is disposed in the second position.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

The following disclosure generally relates to transformable aerial/ground hybrid vehicles, which can perform both aerial and ground modes of locomotion by morphing their configuration with an actuation system also configured to provide propulsion for the vehicle. With the vehicles described in the present disclosure, both aerial and ground modes of locomotion may be performed by morphing the vehicle's configuration and/or geometry with the same actuation system. Additionally, morphing from one mode of locomotion to another is achieved in a relatively simple and robust manner.

Referring toFIGS.1,2, an embodiment of a hybrid aerial/ground transformer robot or multi-modal vehicle (MMV)100is shown. MMV100is generally configured to operate as a quad-rotor in a first or flying mode (shown inFIG.1) and a second or ground locomotion mode (shown inFIG.2). For ground locomotion, MMV100uses actuators to tilt the rotors approximately 90 degrees, so that the rotors act as wheels in the ground locomotion or terrain mode. In the ground mode shown inFIG.2, MMV100may possess superior agility when compared to conventional wheeled robots due to the independent rotational speed or rpm (revolutions per minute) control for each of the wheels or rotors along with the ability to reverse the direction of rotation (bi-directional control) of the wheels. In the embodiment ofFIGS.1,2, MMV100generally includes a vehicle frame or structure102, a control system110mounted to the frame102, a plurality of propulsion elements or rotors120, a plurality of motors125for powering the rotors120, a pair of tilting actuators130, and a pair of actuation mechanisms or assemblies140selectably actuated by actuators130.

A custom control system is utilized to control MMV100in both modes of locomotion. In this embodiment, control system110comprises a processor-sensor board with a 100-200 MHz microprocessor capable of stabilization rates of 1000 Hz; however, in other embodiments, the features of control system110may differ. Control system100also includes bi-directional motor controllers that control motor rpm of motors125as well as change their direction to appropriately accomplish the aerial and ground modes. In this embodiment, control system100further includes an inertial measurement unit and a transceiver. The inertial measurement unit of control system100measures vehicle states used for feedback stabilization. Finally, the transceiver of system100relays wireless information to and from a ground station for data logging as well as issuing motion commands.

MMV100, as well as other vehicles to be described further herein, have many military and civilian applications. For instance, military applications may include intelligence, surveillance and reconnaissance (ISR) missions by using an onboard camera, carry payload using large-scale versions of the present concept, sensing IEDs in battle field, border surveillance, etc. The ability to operate both in air and land may also allow MMV100and other embodiments disclosed herein to be used in other fields, such as space exploration including planetary exploration missions (Mars, Venus, Titan, etc.). MMV100could also complement the capabilities of a Mars rover. Some civilian applications of MMV100could include surveillance in urban areas, package delivery, etc. Embodiments of MMVs disclosed herein, such as MMV100, may be configured to provide functionality similar to quad-copters while also providing ground locomotion.

Referring toFIGS.3-7, another embodiment of an MMV150is shown including a flight or aerial mode or configuration (FIGS.3-5) and a ground or terrain mode or configuration (FIGS.6,7). In the embodiment ofFIGS.3-7, MMV150generally includes a frame or structure152, a power supply or battery155, a control system160, a plurality of actuators or servos170, a plurality of servo arms172, a plurality of connecting links174, a plurality of magnet holders176, a plurality of actuator arms178, a plurality of motor mounts180, a plurality of motors (e.g., DC motors, etc.)185, a plurality of magnets188supported by magnet holders176, a plurality of carbon fiber shafts190, a plurality of rotors or wheels (depending upon the mode of operation)192, and a plurality of carbon fiber connecting rods196. In this embodiment, MMV1150includes four rotors192that are each tiltable approximately 90 degrees for switching between aerial and ground modes of operation. For instance, each rotor192includes a plurality of circumferentially spaced propeller blades193(shown inFIG.3) capable of creating lift sufficient for flying MMV150when rotors192are disposed in a lateral orientation as shown inFIGS.3-5. Additionally, each rotor192comprises an outer rim or cover195coupled to a terminal end of each blade193for transporting MMV150on the ground when rotors192are disposed in a substantially vertical orientation (tilted approximately 90 degrees from the lateral orientation) shown inFIGS.6,7. In this embodiment, servos170are configured to actuate rotors192between their lateral and vertical orientations. The rotors192, which are mounted on shafts190of MMV150, rotate about a pair of first axes181(shown inFIG.6) through which shafts190extend when rotors192are transitioned between the first and second positions, where the pair of first axes181are separate from a plurality of second axes183(shown inFIG.6) about which rotors192rotate when actuated by their respective motors185.

As shown inFIGS.3-5, MMV150is configured to utilize rotors192(labeled as rotors192A,192B,192C, and192D inFIGS.3-7) for flying in a manner similar to a quad-copter. InFIG.5the thrust produced by each rotor192A-192D is denoted by T1, T2, T3, and T4, with thrust T1corresponding to rotor192A, thrust T2corresponding to rotor192B, etc. Additionally, inFIG.5the reaction torques of each of the rotors192A-192D of MMV150are given by Q1, Q2, Q3, and Q4, with reaction torque Q1corresponding to rotor192A, reaction torque Q2corresponding to rotor192B, etc. In this embodiment, the total thrust produced by each rotor192A-192D (e.g., the sum of T1-T4) equals the weight of MMV150while hovering above the ground and the sum of the reaction torques Q1-Q4equals to substantially zero. The body-fixed coordinate system (X, Y, and Z-axes) are indicated inFIG.3. Particularly, forward flight of MMV150corresponds to motion along the X-axis inFIGS.3-7; rotation of MMV150about the X-axis is denoted as roll; rotation of MMV150about the Y-axis is denoted as pitch; and rotation of MMV150about the Z-axis is denoted as yaw.

As shown particularly inFIG.5, diagonally opposite rotor pairs (i.e., rotor192A/rotor192C and rotor192B/rotor192D) rotate in the same direction so that the net moment about the Z-axis (yaw-moment) is at or near zero while MMV150flies. Also, in steady hover or forward flight (e.g., along the X-axis) the thrust vectors (T1, T2, T3, and T4) may be adjusted such that the net moments about the X-axis (roll moment) and the Y-axis (pitch moment) are equal or close to zero. Particularly, the magnitude of each thrust vector T1-T4is varied by changing the rotational speed (rpm) of each individual rotor192A-192D, respectively. The direction of thrust vectors T1-T4may be changed by tilting MMV150(pitch or roll) and/or by tilting just rotors192A-192D relative to the frame152of MMV150using servos170. For example, in order to produce a nose-down pitching motion about the Y-axis, the rotational speed of rotors192A and192B is decreased and those of rotors192C and192D is increased. A nose-down pitch motion of MMV150also results in a forward translation of MMV150along X-axis. As another example, to produce a right roll motion of MMV150(clockwise inFIG.4) about the X-axis, the rotational speed of rotors192A and192D is increased and the rotational speed of rotors192B and192C is decreased. A right roll motion also results in a sideward translation of MMV150along the Y-axis. As a further example, to generate a positive yawing motion of MMV150about the Z-axis, the rotational speed of rotors192A and192C is increased and the rotational speed of rotors192B and192D is decreased. Additionally, the yawing motion results in a change in heading angle of MMV150. In this embodiment, onboard feedback control system160of MMV150is configured to keep MMV150stable in hover and forward flight. In some embodiments, in addition to the inner-loop feedback stabilization provided by control system160, a pilot of MMV150can give higher level commands to fly and maneuver MMV150as desired. The ability to control MMV150by changing the magnitude of four thrust vectors may increase the agility of MMV150in flight.

As shown particularly inFIGS.6,7, to transport MMV150over the ground in the ground locomotion mode, servos170of MMV150tilt the four rotors192A-192D such that they can be used as wheels (via outer rims195of rotors192A-192D) for transporting MMV150along a surface. In this embodiment, a tilting mechanism of MMV150uses a linkage system comprising arms172,174, and178, along with servos170(e.g., linear or rotary servos) to tilt rotors192A-192D and actuate MMV150from the flying mode shown inFIGS.3-5to the ground mode shown inFIGS.6,7. Since the four wheels or rotors192A-192D are actuated by four independent motors185, respectively, differential rotational speed may be used to steer MMV150when MMV150is in the ground mode. As described above, in the flying mode of MMV150, adjacent rotors192A-192D may be rotated in opposite rotational directions for steering MMV150. For instance, rotor192A may be rotated in the opposite direction of rotor192B, and rotors192C and192D rotated in the opposite directions as well. In this manner, MMV150produces a zero yaw moment. However, in the ground mode of MMV150, adjacent rotors192A-192D generally rotate in the same rotational direction to move MMV150forward or backward (e.g., forward and backward along the Y-axis). Therefore, the controllers of control system160for controlling motors185have bi-directional motor control capability.

When steering MMV150on the ground, the rotational speed of rotors192A-192D on one side (e.g., rotors192A and192B, for example) may be increased while the rotational speed of the rotors on the opposing side (e.g., rotors192C and192D, for example) may be decreased. For example, to turn MMV150to the right in the orientation shown inFIGS.6,7(the side of MMV150proximal rotors192C,192D), the rotational speed of rotors192A and192B may be increased while the rotational speed of rotors192C and192D is decreased. As another example, MMV150may make a full, 360 degree turn while remaining stationary by rotating rotors192A and192B in one rotational direction and rotors192C and192D in the opposing rotational direction. The ability to use differential rotational speed for steering MMV150may improve the agility of MMV150when operating in the ground mode. Moreover, when faced by an obstacle rotors192A-192D cannot negotiate, MMV150may transform to the aerial or flying mode shown inFIGS.3-5and thereby fly above and over the obstacle, improving the utility of MMV150in at least some applications.

Referring toFIGS.8,9, another capability of MMV150when MMV150is in the flying mode of operation is the ability to fly forward (e.g., along the X-axis) without tilting frame152forward (e.g., without tiling frame152about the X-axis), unlike a conventional quad-copter. For instance, in some applications, a conventional quad-copter may tilt the whole body of the quad-copter forward in order to fly forward, thereby making the vehicle pitch a function of the forward speed. Therefore, if there is a downward pointing camera attached to the conventional quad-copter, to the camera must be tilted using an active gimbal to keep the camera oriented downward independent of the speed of the conventional quad-copter. However, MMV150may fly forward at relatively high speeds by tilting only two rotors192A-192D (shown inFIG.8) or each of rotors192A-192D (shown inFIG.9) forward, while frame152of MMV150remains horizontal relative to the ground. In other embodiments, rotors192A-192D may be attached to fixed wings mounted to frame152, rotors192A-192D being pivotable about axes parallel with the X-axis shown inFIG.3to provide forward thrust (in the direction of the Y-axis shown inFIG.3) for high speed flight.

In some embodiments, including embodiments at larger scales, MMV150may include a gearbox, such as a two or multiple speed gearbox, to increase the rotational speed of rotors192A-192D when MMV150is in the flying mode while lowering the rotational speed of rotors192A-192D when MMV150is in the ground mode. Additionally, the inclusion of a gearbox allows motors185of MMV150to provide sufficient torque to rotors192A-192D while also maintaining optimal efficiency in both flying and ground modes. In some embodiments, the power required for ground locomotion of MMV150may only comprise a fraction of the power required for the flying mode of MMV150. Although in this embodiment rims195are each coupled to the blades193of a corresponding rotor192A-192D, in a further embodiment, rims195may comprise shrouds or ducts195that do not rotate in concert with blades193about second axes183when MMV150is in the flying mode. Particularly, in this further embodiment, shrouds195act as wheels when MMV150is in the ground mode, but when MMV150is transitioned to the flying mode, blades193rotate relative shrouds195which remain stationary with respect to second axes183, thereby reducing the drag of rotors192A-192D during flight while also increasing the flying efficiency (thrust/power) of the MMV150. Shrouds195may also increase the safety of operating MMV150by shielding blades193, which may be beneficial in larger scale applications where MMV150is configured for transporting human passengers. In this further embodiment, a transmission or clutch may be used to permit relative rotation between shrouds195and the blades193of rotors192A-192D when the MMV150is in the flying mode.

Referring briefly toFIGS.10,11, another embodiment of an MMV200is shown. Particularly, MMV200is shown in a flying or aerial mode inFIG.10and in a ground or terrain mode inFIG.11. MMV200is similar to MMV150described above, and shared features are labeled similarly. However, unlike MMV150described above, MMV200includes rotors or wheels202A-202D which do not include an outer rim or ring (e.g., rims195of rotors192A-192D shown inFIG.3). Moreover, the present disclosure encompasses MMV embodiments having rotors with any number of blades and that may operate with or without an outer rim. In some applications, including more blades per rotor without an outer surrounding rim may improve the mobility of MMV200on highly uneven and loose terrain (e.g., grass, sand, etc.) and extremely smooth surfaces.

Referring toFIGS.12,13, an embodiment of a MMV prototype or technology demonstrator250of the MMV150ofFIGS.3-9is shown. MMV prototype250generally includes a support structure or frame252, a control board or system254, a pair of rotor or wheel tilting mechanisms256, a pair of linear servos or actuators258, a plurality of rotors or wheels260, and a pair of bi-stable, magnetic locking mechanisms262. In the embodiment ofFIGS.12,13, MMV prototype250weighs approximately 16 grams and includes 3-bladed rotors260with a diameter of approximately 1.2 inches; however, in other embodiments, the length and number of blades per rotor260may vary. In this embodiment, the rotors260of MMV250are made out of carbon fiber using a unique fabrication process, as will be discussed further herein, and are capable of producing the required thrust for hover of MMV prototype250. Rotors260are optimized for hover at ultra-low Reynolds numbers through rigorous experimental parametric studies.

In this embodiment, the rotor molds used for fabricating rotors260of MMV250are made in two parts from Polytetrafluoroethylene (PTFE), where the rim of each rotor260is made from a separate mold. In this embodiment, a carbon fiber prepreg is used for fabricating rotors260given that the prepreg may be easily formed and also has a relatively high strength to weight ratio. The rim mold for each rotor260is milled from aluminum in three parts. Particularly, the first part of the rim mold for each rotor260is a disk, the second is a similar disk with a groove cut around the top surface, and the third part is a made of two sub-parts that secure the carbon fiber in the mold. In this embodiment, the blade mold for each rotor260is machined from approximately ⅜″ PTFE and is refined using a milling machine operated by software in accordance with a CAD model of the rotor260. Specifically, the milling machine starts by performing a low resolution cut followed by a finishing toolpath, which smooths the mold into the desired shape. In this embodiment, after the blade molds for each rotor260are milled, the surfaces of the blade molds are smoothened using a utility knife, and a notch is added to a corner to allow the blade mold released.

An embodiment for a process of making the propeller or rotor (e.g., rotors120,192,260, etc.) with the outer ring includes placing two disks of the ring mold together with channel in the middle, and securing the mold with a nut and bolt. The process additionally includes cutting unidirectional carbon fiber prepreg the length of the circumference of the ring plus approximately five millimeters (mm) in the directions of the fibers and with a width of approximately 0.75 mm, tightly wrapping the carbon fiber around the channel of the mold and pressing the ends of the strip together. The process further includes sliding the outer parts of the mold into the channel and clamping both halves together to ensure uniform thickness of the ring. In addition, the process includes placing the mold in an oven at approximately 350° F. for approximately 30 minutes, and removing the mold from the oven to allow the mold to cool. After cooling, the process further includes loosening the nut and separating the disks of the mold to remove the ring.

The process additionally includes cutting the carbon prepreg fabric in the right shape, pressing the prepreg into the male half of the propeller or rotor mold, ensuring that the prepreg is centered in the mold with approximately four to five mm of length at the end of each blade of the rotor. In addition, the process includes placing the ring into the bottom of the ring support in the mold, one blade at a time, folding excess length of the prepreg over the ring and securing it to the inside of the blade. After the prepreg is secured, the process further includes mating the female part of the mold to the male part, and fixing the mold between two aluminum plates with a clamp. Further, the process includes placing the mold into an oven at approximately 350° F. for 90 minutes, removing the mold from the oven and allowing the mold to cool, and sliding a utility knife or another flat tool between the mold halves to release the propeller or rotor. Once the rotor is separated from the mold, the rotor may be finished by removing excess material, boring the center of the rotor and glue the hub in place, placing the rotor on a balancing stand and removing material from the center or ring attachment point until the rotor is balanced, and sharpening the upper and lower surfaces of the leading edges of the blades to improve performance of the rotor. Although a method or process for fabricating a rotor comprising circumferentially spaced blades and a surrounding rim is described above, rotors for MMVs, such as MMV150or MMV prototype250may be fabricated using a variety of methods or processes.

Referring toFIGS.14,15, the tilting mechanism of MMV150shown inFIGS.3-9is shown in greater detail inFIGS.14,15. In the embodiment ofFIGS.3-9,14, and15, the tiling mechanism of MMV150comprises a linkage system with a bi-stable locking mechanism (stabilized via magnets) to lock rotors192A-192D in either vertical (flying mode) or horizontal (ground mode) positions or orientations so that servos170may be powered down once the transformation between the flying and ground modes of MMV150is complete. In other words, due to the bi-stable locking mechanism of the tilting mechanism of MMV150, servos170need only be powered when MMV150is transitioning between the flying and ground modes. In this embodiment, the mechanism is driven using an approximately 1.5 gram micro-linear servo170; however, in other embodiments, MMV150may use a variety of servo actuators for actuating rotors192A-192D between vertical and horizontal positions.

In this embodiment, MMV150includes a pair of bi-stable locking mechanisms for locking rotors192A-192D into the vertical or horizontal positions, where each bi-stable locking mechanism is associated with a pair of rotors192(e.g., rotors192A and192B, for example). As shown particularly inFIG.14, when rotors192A-192D are in the vertical position (relative to the ground) a first magnet188A of the bi-stable mechanism that is coupled to or mounted on a shaft190is attracted by a third magnet188C coupled to or mounted on frame152, thereby holding rotors192A-192D in the vertical position. Then, while transitioning from the vertical position to the horizontal position, servos170apply a torque to each shaft190through the linkage system comprising arms174,176, and178, which releases first magnet188A from the magnetic field of third magnet188C, and rotates shafts190until a second magnet188B coupled to or mounted on shaft190is positioned adjacent third magnetic188C and is thereby attracted by third magnet188C to hold or lock rotors192A-192D in the horizontal orientation shown inFIG.15. This forms a bi-stable mechanism, where first magnet188A is attracted by third magnet188C in one stable state (rotors192A-192D positioned vertically), and second magnet188B attracts third magnet188C in the other stable state (rotors192A-192D positioned horizontally). Thus, first magnet188A and second magnetic188B, each coupled to a shaft190of MMV150, are rotatable relative to third magnet188C, which is stationary relative to the frame152of MMV150. With the bi-stable locking mechanism, servos170may be powered down when not actuating between the flying and ground modes, saving onboard power of MMV150. In this embodiment, there are two servos170, each servo170tilting a pair of rotors192A-192D.

Referring toFIG.16, an embodiment of control system or kinematic autopilot160of MMV150is shown. To assist with controlling and stabilizing MMV150, control system160is generally configured to reduce the weight fraction of the autopilot and avionics units so as to maximize the payload capability and endurance of MMV150. In this embodiment, control system160employs a microprocessor, sensors and speed controllers to achieve a relatively lightweight design with low power and low weight specifications to minimize the structural weight of MMV150.

In the embodiment ofFIGS.16,17, control system160generally comprises a microprocessor or microcontroller unit160A, an inertial measurement unit (IMU)160B, a speed or motor controller unit160C, a wireless transceiver160D, and pinouts160E comprising solder points for transferring commands to motors and servos. A schematic illustrating the transfer of information between the components of control system160is shown inFIG.17. For high power density applications, such as applications of MMV150, the microcontroller unit160A of control system160operates continuously while performing complex calculations (e.g., Kalman filtering and gradient descent attitude estimation, etc.). Microcontroller unit160A also simultaneously provides actuator control inputs at high stabilization rates. Microcontroller unit160A is generally configured to read IMU data from IMU160B, and transfer control commands to speed controller160C, which is in signal communication with the motors185of MMV150, as shown particularly inFIG.17. In this embodiment, microcontroller unit160A comprises a 32-bit ARM Cortex M4 processor that utilizes less than approximately 70 milliamps (mA) of current to operate, and comprises a clock speed of approximately 170 megahertz (MHz) that can service a number of peripherals and can be extended for other sensors and actuators while providing control inputs at approximately 1,000 hertz (Hz).

In this embodiment, IMU160B is generally configured to measure rotational information of MMV150and comprises a nine degree-of-freedom system that includes a three-axis accelerometer, a three-axis gyroscope, and a three-axis magnetometer. IMU160B exhibits internal temperature compensation and has minimal drift in gyroscope measurement as well as low noise characteristics. In this embodiment, attitude estimation and feedback control are carried out using gyro and accelerometer measurements alone. If demanded by a particular application, the magnetometer measurements performed by IMU160B may be used as well in other embodiments.

Speed controller160C of control system160is generally configured to convert control commands from microcontroller160A to motor speed and reverses motor direction when desired. In this embodiment speed controller160C comprises a field effect transistor, diodes, resistors and capacitors packaged into a compact unit that can continuously output upward of approximately 1.5 amps (A) to each motor185of MMV150. In this embodiment, the avionics unit of MMV150comprises two speed controller units160C with each unit160C servicing two motors (e.g., motors185). In this arrangement, the voltage polarity of the motor185leads may be conveniently switched in response to a digital signal from the microcontroller160A of control system160, thereby providing the bi-directional capability for the operation of MMV150.

Transceiver160D of control system160is generally configured to receive pilot commands and transmit vehicle flight information for data logging. For instance, transceiver160D may accept wireless inputs from a remote ground station162(shown inFIG.17) as well as transfer sensor information for data logging. In this embodiment, transceiver160D comprises a 2.4 gigahertz (GHz) wireless transceiver that supports up to approximately 250 kilobits per second (kbps) of air data rate while consuming less than approximately 20 mA of current. Additionally, in this embodiment, transceiver160D of control system160includes a surface mount chip antenna with a gain of approximately −0.5 decibels isotropic (dBi) to conserve space and to minimize losses. Further, in in this embodiment, control system160includes a power regulator or switching voltage regulator to provide over-voltage protection and to supply approximately 3.3 volts (V) to the various hardware units. The power regulator of this embodiment of control system160may accept input voltages of up to approximately 17 V with sufficient current output capability. In this embodiment, microcontroller160A has several general purpose input-output (GPIO) pins and each of the devices of control system160communicate using specific GPIO pins assigned to them. Additionally, in this embodiment, the IMU160B, speed controller160C and wireless transceiver160D talk with the microprocessor through inter-integrated circuit, timers and serial peripheral interface protocols respectively. Although in this embodiment MMV150includes a control system160having microcontroller unit160A, IMU160B, a speed controller unit160C, and wireless transceiver160D, in other embodiments, the features and characteristics of the control system of MMV150may vary.

In this embodiment, when in the flying mode, the IMU160B of control system160measures the attitude and angular rates of MMV150are processed by the microcontroller160A and a control input is generated to each motor185of MMV150using a proportional derivative feedback controller with tunable gains executed by microcontroller160A. As illustrated inFIG.3, rotors192A and192C spin in counterclockwise direction and rotors192B and192D spin in clockwise direction. However, during the transition of MMV150to the ground mode of operation, the rotors192C and192D of MMV150are reversed in their direction and the angular speed of rotors192C and192D is decreased substantially (e.g., ten times lower angular speed than the flying mode in some embodiments).

In an embodiment, microcontroller unit160A of control system160communicates with the speed control unit160C through two control signals that determine magnitude of rotational speed and direction of the rotors192A-192D, with power supplied from battery155of MMV150. Additionally, in this embodiment, when in the ground mode of operation, microcontroller unit160A of control system160transmits pulse-width-modulated signals to servos170that rotate rotors192A-192D about shafts190by approximately 90 degrees. Therefore, by appropriately modulating the signals transmitted by microcontroller unit160A, specific control movements in the flying as well as ground modes may be achieved. Table 1 below provides an exemplary summary of the various control signal states in each of these modes for this embodiment, with rotor192A labeled “Rotor1,” rotor192B labeled “Rotor2,” etc. It is noted that the direction of rotation of rotors192A-192D is fixed in the flying or aerial mode of this embodiment but can be reversed as desired in land mode to actuate forward and backward motions as well as turns.

In some embodiments, control system160comprises a circuit board designed using a four layer approach. In this embodiment, the power and ground layers are embedded between the top and bottom layers to improve compactness. In this embodiment, the signals have a minimum trace width of approximately 0.004 inches (in), the power signals with a trace width of approximately 0.008 in and the wires communicating wireless signals (RF) had a width of 0.032 in; however, in other embodiments, the circuit board design of control system160may vary. In some embodiments, thicker tracks may be used for the power lines of the circuit board to address potential issues associated with voltage drops and heating of the power lines. In certain embodiments, the radio frequency (RF) signal wires may be treated by keeping the RF signal wires on the top side of the circuit board and avoiding usage of any through-holes. Placement of components directly underneath RF components may also be avoided in some embodiments. In this embodiment, direct access to all of the signal pins of control system160is provided for space and weight optimization. In this embodiment, the circuit board of control system160is manufactured using standard FR-4 material with approximately 1 ounce copper thickness. Additionally, in this embodiment, the circuit board of control system160(with populated components) weighs approximately 1.5 grams; however, in other embodiments, the mass and process of manufacturing the circuit board of control system160may vary.