Variable referenced control system for remotely operated vehicles

A frame of reference is selected, and control inputs provided by a vehicle operator are transformed to account for the orientation of a remotely operated vehicle with respect to the selected frame of reference such that the remotely operated vehicle responds to the control inputs with respect to the selected frame of reference. An earth frame of reference may be selected based on a fixed true heading, e.g., North, or based on the initial orientation of the vehicle operator. Alternatively, a vehicle frame of reference may be selected which provides a fixed frame of reference with respect to the vehicle and a variable frame of reference with respect to the vehicle operator. A vehicle operator frame of reference may also be selected based on the orientation of the vehicle operator with respect to earth, and control commands are transformed based on changes in both the operator orientation with respect to the earth reference and the remotely operated vehicle orientation with respect to the earth reference, which provides a fixed frame of reference with respect to the vehicle operator and a variable frame of reference with respect to the vehicle. The remotely operated vehicle heading transformation may be based on a selected forward, fixed or variable point on the vehicle related to a vehicle center of gravity, a forward part of the vehicle, the location of a sensor on the vehicle, or some other arbitrary reference location on the vehicle.

TECHNICAL FIELD 
The present invention relates to the control of remotely operated vehicles, 
and more particularly to a variable reference for the control of a 
remotely operated vehicle. 
BACKGROUND OF THE INVENTION 
There are a variety of uses for remotely operated vehicles including 
military, industrial and entertainment/recreation applications. For 
entertainment/recreation applications, remotely operated model airplanes, 
helicopters, automobiles, ships and sail boats are well known. In an 
industrial application, it is well known to use a remotely operated 
vehicle to complete high risk or difficult tasks such as inspection, 
maintenance and repair in a high radiation area, exploration of extreme 
water depths, and airborne surveillance. 
Within the military spectrum, there has been a recent resurgence in the 
interest in unmanned aerial vehicles (UAVs) for performing a variety of 
missions where the use of manned flight vehicles is not deemed 
appropriate, for whatever reason. Such missions include surveillance, 
recognizance, target acquisition and/or designation, data acquisition, 
communication data linking, decoy, jamming, harassment, or one way supply 
flights. Similarly, it has long been the practice of remotely controlling 
torpedo's for underwater delivery of ordinance. 
An obvious difference between a manned and remotely operated vehicle 
relates to the control or pilotage of the vehicle. In a manned vehicle, 
the operator sits within the vehicle and inputs control signals related to 
the desired vehicle response. In such a case, all requests by the vehicle 
operator are based on a vehicle frame of reference. For example, in an 
aircraft, control requests are typically input by a pilot via a control 
stick. If the pilot wishes to move the aircraft forward, he inputs a 
forward movement of the control stick, which pitches the aircraft in the 
forward direction. Similarly, if the pilot wishes to move the aircraft to 
the right, he inputs a right lateral stick motion which, in turn, rolls 
the aircraft to the right. 
A problem associated with operating remotely operated vehicles is that when 
the vehicle operator controls the vehicle from a distant location, 
commands referenced to the operator's body or operator frame of reference 
may result in undesired vehicle motion. Typically, the motion of a 
remotely operated vehicle is governed by the direction in which a fixed 
reference point or axis on the vehicle is pointing, e.g., the direction 
that the vehicle nose or front is pointing. Referring to the example of 
FIG. 1, if the vehicle operator 10 and the vehicle 12 have the same 
forward orientation or frame of reference, then control inputs by the 
vehicle operator 10 will result in a corresponding change in vehicle 
motion, e.g., if the vehicle operator commands a right motion of the 
vehicle, the vehicle 12 will move/turn to the right. However, as shown in 
the example of FIG. 2, if the vehicle is moving towards the vehicle 
operator 10 then a control input by the vehicle operator will result in 
opposite motion of the vehicle, e.g., if the vehicle operator commands a 
right motion of the vehicle, the vehicle will actually move/turn left with 
respect to the vehicle operator. 
Therefore, existing methods for controlling remotely operated vehicles rely 
greatly on operator skill. With a considerable amount of training, an 
operator can learn to operate a remotely operated vehicle proficiently in 
most spatial relationships of the vehicle with respect to the operator. 
However, under high workload and stress conditions, the non-intuitive 
control of a remotely operated vehicle may result in inadvertent and 
unwanted motion of the remotely operated vehicle. 
DISCLOSURE OF THE INVENTION 
Objects of the invention include the provision of an improved control 
system for controlling a remotely operated vehicle which provides a 
variable frame of reference for control of the remotely operated vehicle. 
Another object of the present invention is to provide a control system for 
a remotely operated vehicle which allows a vehicle operator to select a 
vehicle reference axis for purposes of determining the control response of 
the vehicle. 
A further object of the present invention is to provide a vehicle control 
system for a remotely operated vehicle which allows the vehicle operator 
to select between a vehicle frame of reference, an earth frame of 
reference, and a variable frame of reference for controlling the operation 
of a remotely operated vehicle. 
According to the present invention, a frame of reference is selected, and 
control inputs provided by a vehicle operator are transformed to account 
for the orientation of a remotely operated vehicle with respect to the 
selected frame of reference such that the remotely operated vehicle 
responds to the control inputs with respect to the selected frame of 
reference. 
In further accord with the present invention, an earth frame of reference 
may be selected based on a fixed heading, e.g., North, or based on the 
initial orientation of the vehicle operator. Alternatively, a vehicle 
frame of reference may be selected which provides a fixed frame of 
reference with respect to the vehicle and a variable frame of reference 
with respect to the vehicle operator. A vehicle operator frame of 
reference may also be selected based on the orientation of the vehicle 
operator with respect to earth, and control commands are transformed based 
on changes in both the operator orientation with respect to the earth 
reference and the remotely operated vehicle orientation with respect to 
the earth reference, which provides a fixed frame of reference with 
respect to the vehicle operator and a variable frame of reference with 
respect to the vehicle. 
In still further accord with the present invention, the remotely operated 
vehicle heading transformation may be based on a selected forward, fixed 
or variable point on the vehicle related to a vehicle center of gravity, a 
forward part of the vehicle, the location of a sensor on the vehicle, or 
some other arbitrary reference location on the vehicle. 
The present invention provides a simplified control of a remotely operated 
vehicle by allowing the vehicle operator to select a frame of reference 
for control signals based on a vehicle operator reference or a fixed earth 
reference as opposed to a vehicle reference. A fixed earth reference is 
particularly useful when controlling vehicle motion based on the indicated 
location of the vehicle on an electronic map, the map having a fixed earth 
frame of reference. Therefore, the invention allows an unskilled or 
relatively inexperienced operator to control a remotely operated vehicle 
without the associated disorientation when the vehicle movements become 
non-intuitive, as in the prior art. Additionally, by allowing the remotely 
operated vehicle heading transformation to be based on the location of a 
sensor on the vehicle, the vehicle may be controlled such that variations 
in control inputs will control the pointing direction of the sensor. 
The foregoing and other objects, features and advantages of the present 
invention will become more apparent in the following detailed description 
of exemplary embodiments thereof, as illustrated in the accompanying 
drawings.

BEST MODE FOR CARRYING OUT THE INVENTION 
The variable referenced control system for a remotely operated vehicle of 
the present invention is particularly well suited for allowing the optimum 
control of a remotely operated vehicle based on both operator and mission 
considerations. The system provides for the referencing of vehicle 
commands based on an operator frame of reference so that control commands 
provided by the operator remain intuitive and independent of the 
orientation of the vehicle with respect to the operator. Additionally, the 
system provides for the referencing of vehicle position based on a vehicle 
sensor, thereby allowing the operator to easily control the pointed 
direction of a sensor on the vehicle for improved accuracy in the receipt 
of intelligence. A further advantage of providing a fixed reference for a 
remotely operated vehicle is the ease of controlling the vehicle when the 
position of the vehicle is indicated on an electronic map having a fixed 
frame of reference. 
The present invention will be described in the context of an unmanned 
aerial vehicle (UAV). However, it will be understood by those skilled in 
the art that the variable referenced control system of the present 
invention may be applied to any remotely operated vehicle provided that 
the vehicle contains a navigation system or other means for determining 
changes in vehicle orientation with respect to an operator or fixed frame 
of reference. 
Referring to FIG. 3, one embodiment of an UAV 100 is shown. The UAV used in 
the example of the present invention comprises a toroidal fuselage or 
shroud 20 having an aerodynamic profile, flight/mission equipment 30, a 
power plant subsystem 50, and a rotor assembly 60. The toroidal fuselage 
20 is provided with a plurality of support struts 24 which are attached to 
the rotor assembly 60 and are operative to supported the rotor assembly 60 
in fixed coaxial relation with respect to the toroidal fuselage 20. The 
toroidal fuselage 20 contains forward located internal bays 26 which are 
typically utilized for sundry flight/mission equipment 30 as described 
herein below. Mission payload equipment 32 is preferably located, but not 
limited to, the internal bay 26. Generally the mission payload equipment 
32 will consist of some types of passive sensors, e.g., infrared 
detectors, television cameras, etc., and/or active devices, e.g., lasers, 
radio communications gear, radar, etc., and the associated processing 
equipment. Other flight/mission equipment 30 such as avionics 34, 
navigation equipment 36, flight computer 38, communications gear 40 (for 
relaying real time sensor data and receiving real time command input 
signals), antenna, etc., are distributed in the various internal bays 26 
as shown for example in FIG. 1. Distribution of the various flight/mission 
equipment 30 is optimized in conjunction with the placement of a power 
plant subsystem 50 within the toroidal fuselage 20. 
The flight/mission equipment 30 described thus far is exemplary of the type 
which may be used in a UAV. However, as will be understood by those 
skilled in the art, a separate flight control computer, avionics, and 
navigation system are not necessarily required in order to perform the 
functions identified in the present invention. Alternatively, a single 
flight control computer or mission computer may be provided to perform the 
above identified functions. 
Referring to FIG. 4, a control panel 200 for remote operator control of the 
UAV 100 (FIG. 1) is shown. The control panel 200 is provided with a joy 
stick or control stick 205 for providing control inputs to control the 
operation of the UAV. The control stick 205 is shown as being a two axis 
control stick wherein forward and aft movement of the control stick 
relates to pitch, and side-to-side movement of the control stick related 
to roll. A control panel computer 209 is provided for receiving the 
control commands provided by the control stick 205 and converting them 
into is signals to be transmitted via by communications equipment 212. The 
communications equipment 212 comprises a transmitter 215 for receiving the 
control commands provided from the control panel computer 209 and for 
transmitting the control commands via a control panel antenna 220. 
Referring now to FIG. 5, when control signals are transmitted by the 
control panel via the antenna 220, the signals are received by the UAV 
antenna 42 and thereafter provided to the UAV communications equipment 40. 
The communications equipment comprises a receiver 46 and a 
demodulator/decoder 48 for receiving and decoding the received signals 
transmitted by the control panel. Thereafter, the demodulated and decoded 
control signals are provided to the flight control computer 38 and 
avionics equipment 34. The flight control computer 38 and avionics 
equipment 34 process the incoming control signals to thereby provide the 
appropriate control surface commands to the UAV control surfaces to 
perform the desired maneuvers. 
All of the apparatus described thus far is exemplary of that which is known 
in the art. In a vehicle referenced control system of the prior art, a 
fixed reference point or location on the vehicle frame is selected as 
forward or the head of the vehicle, and in response to control signals, 
that reference point is maneuvered. Therefore, for example, if the 
operator inputs a right turn or roll command via the control panel, the 
UAV will turn the fixed reference point to the right, relative to the UAV 
frame of reference. However, depending on the orientation of the UAV with 
respect to the operator, a right turn command input by the operator at the 
UAV controller may look like a left turn to the operator if the UAV is 
heading towards the operator or if the UAV is "behind" the operator. 
The variable referenced control system of the present invention allows the 
operator to select various different frames of reference for controlling 
the UAV, thereby allowing the operator to tailor the UAV control to the 
specific mission or operational requirements, and thereby provided for a 
simplified, intuitive control. 
Referring to FIG. 6, the flight control computer is provided with a stick 
transformation function 400 which allows the operator to select between a 
variety of control references for controlling the remotely operated 
vehicle. A specific reference may be selected by repositioning a switch or 
entering a command on the control panel 200 (FIG. 2). Thereafter, the 
reference command is provided via the communications equipment and control 
panel antenna to the flight control computer via the communications 
equipment on the remotely operated vehicle. 
The stick transformation function 400 is responsive to control signals 
received from the control panel and vehicle heading information for 
controlling the vehicle in accordance with the desired mode and reference. 
The pitch command (provided from the control panel via the vehicle 
communications equipment) is provided on a line 405 to a pitch axis 
transformation function 410 and a roll axis transformation function 412. 
Similarly, the roll command is provided on a line 415 to the pitch axis 
transformation function 410 and the roll axis transformation function 412. 
The other input to the pitch axis transformation function 410 and the roll 
axis transformation function 412 is a transformation angle (.theta.). The 
transformation angle is determined based on the true heading of the 
vehicle as determined by the navigation system 36 and the desired vehicle 
reference and vehicle reference mode. 
The vehicle's true heading is provided from the navigation equipment 36 on 
the vehicle, e.g., a ring laser gyro or an inertial navigation system. The 
true heading signal is indicative of the orientation of a fixed point on 
the aircraft with respect to true north. Typically, the reference point on 
the vehicle is determined to be the forward section on the vehicle as 
determined by design or other method such as using a center of gravity 
calculation. The center of gravity is used for the toroidal shape because 
the forward flight characteristics of the vehicle are improved. The true 
heading signal provided by the navigation system 36 is provided on a line 
420 to a summing junction 425. The other input to the summing junction 425 
is a reference heading signal on a line 460 which is provided as the 
output of a summing junction 450. 
One input to the summing junction 450 is a vehicle reference signal on a 
line 435 provided by a vehicle reference switch 445. The operation of the 
vehicle reference switch 445 is dependent upon the position of a control 
panel vehicle reference switch 245 on the control panel 200 (FIG. 4). If 
the control panel vehicle reference switch 245 is in the forward reference 
position, then the vehicle reference for purposes of vehicle control is 
the forward reference position on the aircraft. However, if the control 
panel vehicle reference switch 245 is in the sensor reference position 
then control of the vehicle will be based on the sensor position on the 
vehicle. Therefore, the signal on the line 435 will be equal to the 
angular position between the forward position on the vehicle and the 
sensor position on the vehicle. The angular position between the forward 
position on the vehicle and the sensor position on the vehicle is defined 
as an offset angle (.phi.). The other input to the summing junction 450 is 
a reference mode signal on a line 453 provided by a reference mode switch 
457. The operation of the reference mode switch 457 is dependent upon the 
position of a control panel reference mode switch 257 on the control panel 
200 (FIG. 4). In a vehicle reference mode, the vehicles reference axis is 
used for purposes of controlling the vehicle from the control panel. In a 
map reference mode, an earth reference, such as North, is used for control 
of the vehicle. In an operator reference mode, the orientation of the 
operator upon activation of the operator mode is used as the reference 
axis. The output of the summing junction 450 is the reference heading 
signal on line 460 which is provided to the summing junction 425. The 
output of the summing junction 425 is the transformation angle, and is 
provided on a line 467 to the pitch axis transformation 410 and the roll 
axis transformation 412. 
The pitch axis transformation 410 uses equation 1 below for determining a 
transformed pitch stick signal (TPSS) to be provided on the line 470 to 
the pitch flight control system: 
EQU TPSS=pitch command * cos(.theta.)-roll command * sin(.theta.)(eq. 1) 
Similarly, the roll axis transformation 412 using equation 2 below to 
provide a transformed roll stick signal (TRSS) on a line 475 to the roll 
flight control system: 
EQU TRSS=roll command * cos(.theta.)+pitch command * sin(.theta.)(eq. 2) 
The operation of the invention is best understood by example. When the 
vehicle is being operated in the normal mode wherein the vehicle reference 
is the forward vehicle axis and in the vehicle reference mode, then the 
transformation function should not make any change in the pitch command 
405 and roll command 415 being provided to the lines 470 and 475, i.e., 
TPSS=pitch command and TRSS=roll command. The vehicle heading signal is 
provided on the line 420 to the summing junction 425. The forward 
reference signal, which is zero, is provided on the line 435 to the 
summing junction 450. Additionally, in the vehicle reference mode, the 
vehicle heading is provided via the switch 457 on the line 453 to the 
summing junction 450. The output of the summing junction 450 is the 
vehicle heading on the line 460 which is subtracted from the vehicle 
heading signal on the line 420 in the summing junction 425. Therefore, the 
output of the summing junction 425 is zero on the line 467, and referring 
to equations 1 and 2, TPSS on the line 470 is equal to the pitch command 
on the line 405 and TRSS on the line 475 is equal to the roll command on 
the line 415 when the transformation angle is equal to zero. 
When the vehicle is operating with a sensor reference in the vehicle 
reference mode, control inputs by the operator will cause the position of 
the vehicle sensor to change with respect to a vehicle frame of reference. 
In FIG. 6, the switch 445 will be in the sensor reference position, and a 
signal indicative of the angular position of the sensor with respect to 
the forward reference axis of the vehicle is provided on the line 435 to 
the summing junction 450, the other input to the summing junction 450 
being the vehicle heading signal on the line 453. Therefore, the 
transformation angle will be the sensor reference angular position on the 
line 467. Therefore, TPSS and TRSS will be transformed by an amount 
corresponding to the angular position of the sensor reference with respect 
to the forward reference axis of the vehicle in the transformation 
functions 410, 412. 
The map reference mode of operation is particularly useful when controlling 
the position of the vehicle using an electronic map, the electronic map 
having a fixed frame of reference, e.g., North. In this case, both the 
operator control panel and the vehicle operate with respect to the fixed 
frame of reference. During operation with a vehicle forward reference in 
the map reference mode, the output of the summing junction 450 is a signal 
indicative of the selected reference, e.g., North. Therefore, the 
transformation angle output from the summing junction 425 will be 
indicative of the difference between vehicle heading and the reference 
heading. In equations 1 and 2, the pitch command and roll command are 
transformed based on the difference between the aircraft heading and the 
map reference heading. If the map reference mode is used with a sensor 
reference, then the angular position of the sensor with respect to the 
vehicle forward reference axis is added to the map reference in the 
summing junction 450. Therefore, the transformations 410,412 will also 
account for the angular difference between the sensor and the vehicle 
forward reference axis during the transformation of the pitch command and 
the roll command. 
The operation of the operator reference mode illustrated in FIG. 6 is 
basically identical to the operation of the map reference mode illustrated 
in FIG. 6, except that the reference axis for purposes of transformation 
is based on the orientation of the operator control panel upon activation 
of the operator reference mode. Therefore, if the operator is facing North 
upon activation of the operator mode, the North reference will be provided 
on the line 453. 
A problem associated with a fixed operator reference during operation in 
the operator reference mode is that if the operator changes position 
during remote operation of the vehicle, the fixed frame of reference no 
longer provides the advantage of intuitive roll and pitch commands. To 
overcome this short coming, a variable operator reference mode may be 
provided wherein the operator reference changes based upon changes in the 
orientation of the operator control panel. This may be accomplished by 
mounting the operator control panel on a pedestal and providing a servo or 
gyro signal indicative of the change in the position of the control panel 
With respect to the initial operator reference. Alternatively, the 
operator control panel may be provided with a precise position indicator 
such as a ring laser gyro or inertial position system so that changes in 
the position of the control panel will result in changes in the operator 
reference position. 
The present invention was described in the context of an unmanned aerial 
vehicle because of the more complex control associated with airborne 
vehicles. However, it will be understood by those skilled in the art that 
the variable referenced control system of the present invention is 
applicable to any remotely operated vehicle provided that means are 
provided to determine the orientation of the vehicle with respect to the 
selected reference. The vehicle may be provided with an onboard navigation 
system, or means may be provided to externally sense the orientation of 
the vehicle with respect to the reference axis. 
Although the invention has been described and illustrated with respect to 
exemplary embodiments thereof, it should be understood by those skilled in 
the art that the foregoing and various other changes, omissions, and 
additions may be made therein and thereto, without departing from the 
spirit and scope of the present invention.