Vehicular Guidance Systems With Single Axis Control Patents (Class 318/580)
  • Patent number: 4940925
    Abstract: A visual navigation system provides absolute position information to multiple automatically guided vehicles (AGVs) such as mobile robots. The beacon-equipped AGVs emit light visible to overhead television cameras. The beacons are arranged and controlled so that the vision systems can acquire, measure, and report the locations of multiple AGVs. The system controller incorporates a programmable "factory map", or knowledge base, of allowable paths of travel for the AGVs, which navigate by dead reckoning with periodic position updates from the visual navigation system. The visual navigation system notifies the autonomous AGVs and the system controller when an AGV strays from its command path. The combination of computer controls in the elements of the system provides the means to stop and to recover straying AGVs. The navigation system visually monitors normal AGV travel, off-course corrections, "lost" AGV searches, and recovery. Thus, it provides closed-loop, servo-like operation.
    Type: Grant
    Filed: October 31, 1988
    Date of Patent: July 10, 1990
    Assignee: Texas Instruments Incorporated
    Inventors: Martin A. Wand, Anh V. Ho, Chuan-Fu Lin, Phen-Lan Huang, John P. Williston, Haradon J. Rice, Thomas J. Doty
  • Patent number: 4926103
    Abstract: The invention is a method of dynamic collision avoidance for multiple automatically guided vehicles (AGVs) on bidirectional paths. It calculates windows, or areas of computer memory, against which it matches the reported positions of AGVs. The invention acts on information from a central data base in which the factory or operating space of the AGVs is mapped and from AGV position updates supplied by an independently operating visual navigation system. The invention dynamically calculates the locations and dimensions of the windows for each position update. Since these position updates occur in real time, many times each second, the invention provides the means for the AGV system's controller to prevent collisions between the AGVs and other objects without minimizing the degrees of freedom of AGV movement.
    Type: Grant
    Filed: October 31, 1988
    Date of Patent: May 15, 1990
    Assignee: Texas Instruments Incorporated
    Inventors: David F. Summerville, John P. Williston, Martin A. Wand, Thomas J. Doty, Haradon J. Rice, Phen-Lan Huang
  • Patent number: 4924153
    Abstract: An apparatus for controlling the position and posture of a moving body for inspecting the dust proofing properties of a plurality of filters is disclosed. Marks placed on the filter frames are visually recognized, the position and posture of the unmanned moving body relative to the marks is calculated and controlled to move the unmanned moving body in a predetermined manner.
    Type: Grant
    Filed: April 7, 1989
    Date of Patent: May 8, 1990
    Assignee: Kabushiki Kaisha Komatsu Seisakusho
    Inventors: Suzuki Toru, Atsuhiko Kato, Mitsuo Hosoi, Ichiro Nakano
  • Patent number: 4918362
    Abstract: An industrial truck comprising at least one steerable wheel is to be guided in dependence on direction-controlling signals which are transmitted to the industrial truck. At a junction the truck receives a direction-controlling steering signal, which causes the at least one steerable wheel to be laterally offset from the guiding signal line until a signal equilibrium which depends on the offset has been established in the steering controller. In dependence on the distance traveled and/or on time, a resetting signal is received which causes the steering means to return to an operating condition in which the vehicle is centered over a signal guiding line to be followed. The signals are transmitted by a guiding signal line, which is buried in the ground and cooperates with a sensor, which is provided at the center of the vehicle and scans the guiding signal line so as to control the deflection of steerable wheels of the vehicle.
    Type: Grant
    Filed: December 15, 1988
    Date of Patent: April 17, 1990
    Assignee: Firma Jungheinrich Unternehmensverwaltung KG
    Inventors: Sven Christensen, Rolf Haelbich, Jurgen Hanel, Siegfried Hoener, Volker Pridat
  • Patent number: 4902948
    Abstract: A guidance system for guiding a plurality of unmanned vehicles along guide wires. A plurality of data communication circuits are provided which form an extensive network. A traffic control computer composes a coded vehicle instruction for assigning tasks and allocates resources to said unmanned vehicles. The traffic control computer polls the status of each vehicle at varying time intervals and receives a response from said vehicle.The network connecting the computer and the communication circuits prevents reception of data transmissions from more than one vehicle at a time. Other messages are temporarily stored.Data transmitters generate low frequency, low power signals which have a high data transmission rate.Digital data is converted at the transmitters into cosine waveforms of selected frequencies. The cosine waveforms are transposed into sine waveforms at receivers. Low impedance or high impedance characteristics are imposed upon the guide wires.
    Type: Grant
    Filed: July 1, 1988
    Date of Patent: February 20, 1990
    Assignee: Eaton-Kenway, Inc.
    Inventors: Leigh E. Sherman, Gary L. Whatcott, Richard M. Dicks, David C. Madsen
  • Patent number: 4885514
    Abstract: An arrangement for controlling the position of a movable member, especially an aircraft control surface member, includes an operational amplifier and a capacitor connected in parallel to the amplifier. The control arrangement further includes a detector which detects the restoration of the supply of electric power following its interruption and generates a limited-duration pulse. This pulse is then used to close a switch, which is interposed between an input terminal of the capacitor and the ground, for the duration of this pulse, so that the capacitor is charged much more rapidly than otherwise. The output signal of the combination of the operational amplifier and the capacitor is supplied to an actuator for the movable member so that the extent of excursion of the movable member out of its desired position after the electric power supply has been restored is minimized.
    Type: Grant
    Filed: December 24, 1987
    Date of Patent: December 5, 1989
    Assignee: United Technologies Corporation
    Inventors: Ari M. Novis, Don L. Adams, Troy J. LaMontagne, Albert Sivahop
  • Patent number: 4878003
    Abstract: A method and an apparatus for automatically steering a vehicle intermittently associated with a stationary guide structure. A sensor detects the distance between the vehicle and the guide structure to provide an actual value signal, which is compared with a reference signal to effect feedback control over vehicle movement. The referenece signal is adjustably controlled periodically when required, e.g., when the vehicle has completed a circuit within the area of interest.
    Type: Grant
    Filed: June 10, 1987
    Date of Patent: October 31, 1989
    Inventor: Hans-Reinhard Knepper
  • Patent number: 4862047
    Abstract: This invention is intended to periodically correct the position and posture of an automatically steerable unmanned moving body according to a guiding method with the aid of dead reckoning or the like. A plurality of sets of at least two ground marks (8) are placed on the movement passage of the unmanned moving body (1) in a spaced relation along a reference passage (15) and the ground marks (8) are visually recognized by means of a television camera (6) or the like mounted on the unmanned moving body. Then, the existent position and posture of the unmanned moving body (1) are detected with reference to the results of visual recognization and thereafter the position and posture of the unmanned moving body (1) which have been calculated in accordance with the aforesaid guiding method or the like are corrected in accordance with the thus detected results.
    Type: Grant
    Filed: January 20, 1988
    Date of Patent: August 29, 1989
    Assignee: Kabushiki Kaisha Komatsu Seisakusho
    Inventors: Toru Suzuki, Atsuhiko Kato, Mitsuo Hosoi, Ichiro Nakano
  • Patent number: 4800978
    Abstract: An improved magnetic object detecting system having high sensitivity and noise immunity is disclosed.The detection system is of the type having a stimulation coil for generating a magnetic field and a pair of magnetic field detection coils, and the stimulation coil is of a magnetic core type employing a magnetic core.
    Type: Grant
    Filed: November 8, 1985
    Date of Patent: January 31, 1989
    Assignee: NEC Corporation
    Inventors: Yasuhiro Wasa, Yojiro Kondo, Tokuki Miura
  • Patent number: 4751443
    Abstract: A servo system simulator utilizing an electronic equivalent of the servomotor to drive a programmable electronic load which mimics the actual load encountered by the servo system simulated.
    Type: Grant
    Filed: July 22, 1986
    Date of Patent: June 14, 1988
    Assignee: Honeywell Inc.
    Inventors: Joseph W. Jackson, Theodore C. Ebbinga
  • Patent number: 4680465
    Abstract: A force controller wherein lateral, axial and rotational force on a handle (10) are opposed by bending, extension, compression and torsional forces in a tubular flexure element (12) that includes lateral rings (92a . . . 92n) and longitudinal beams (96a . . . 96n-1). A translating plate (23) is controlled in accordance with the torsion and deflection of flexure element (12) to provide optical control signals from code element (56) and read head (64) for three axes of motion. Axial forces on handle (10) cause extension or compression of flexure element (12) which is linked to fin (42). Pivotal movement of fin (42) in response to such extension and compression provides optical control signals from code element (72) and read head (74) for a fourth axis of motion.
    Type: Grant
    Filed: April 23, 1984
    Date of Patent: July 14, 1987
    Assignee: Parker Hannifin Corporation
    Inventor: Curtis E. Stevens
  • Patent number: 4583030
    Abstract: Aircraft attitude along the pitch axis is controlled by inputting a velocity command to a pitch control subsystem that includes a velocity side channel and a gain side channel of a pitch servo amplifier. An output from each channel of the pitch servo amplifier is applied to a pitch servo motor for positioning a primary control surface. The velocity of the pitch servo motor is detected by a velocity detector that generates a velocity feedback signal and control signals for each channel of the pitch servo amplifier. Also responsive to the velocity signal of the detector is a pre-flight test circuit for pre-flight checkout of the pitch control subsystem. In each line from the output of the channels of the pitch servo amplifier is a current detector that is part of a pitch trim control subsystem that responds to the current through the pitch servo motor to generate a trim velocity command signal. This velocity command signal is input to a velocity side channel and a gain side channel of a trim servo amplifier.
    Type: Grant
    Filed: August 3, 1982
    Date of Patent: April 15, 1986
    Assignee: Century Flight Systems, Inc.
    Inventor: John M. Nixon
  • Patent number: 4580210
    Abstract: In a control system having a manipulatable unit, such as an aircraft stick, which is biased toward a neutral position to provide control "feel", an input which at each instant signifies the position of displacement of the stick from its neutral position is processed to provide an output signifying the magnitude of the biasing force to be applied to the stick. In a range of positions spaced to one side of its neutral position (or in such a range at each side of neutral) the output provides for a steep biasing force gradient as the stick is moved through a predetermined distance in either direction from a turning point to which the stick had been brought by movement in the opposite direction. For all other movements of the stick within that range the biasing force has a low gradient. The higher gradient of bias for small trimming movements provides better feel for trimming without requiring stick bias to be unduly stiff during coarser stick displacements.
    Type: Grant
    Filed: April 17, 1984
    Date of Patent: April 1, 1986
    Assignee: Saab-Scania Aktiebolag
    Inventor: Lennart Nordstrom
  • Patent number: 4531080
    Abstract: A controller for producing electrical control signals has a relatively stationary supporting section providing an upwardly facing hand supporting surface and an upward projection, and has a stick-like control section mounted on a first gimbal joint on top of the projection, to swing about pitch and roll axes. A second gimbal joint is spaced along the roll axis from the first one and rotates about said roll axis and about a gimbal axis parallel to the pitch axis. A gimbal ring of the first joint is rigidly connected to a gimbal member of the second joint for unison rotation about the roll axis. A second gimbal member of the second joint is caused to rotate about said gimbal axis in unison with swinging of the control section about the pitch axis by a linkage connection between them. A signal generator for each of the pitch and roll axes and a stick force generating means for each of those axes are connected with respective gimbal members of the second joint.
    Type: Grant
    Filed: May 13, 1983
    Date of Patent: July 23, 1985
    Assignee: Saab-Scania Aktiebolag
    Inventors: Lennart Nordstrom, Tommy Savstrom
  • Patent number: 4463297
    Abstract: A controller is described for limiting the rate and acceleration of a device positioned by at least one actuator which responds to a sequence of position commands separated by time intervals incorporating a subtractor for taking the difference of two consecutive position commands to provide a difference signal in vector form, means for determining the magnitude of the difference signal, a comparator for comparing the magnitude of the difference signal with a predetermined value, a switch for coupling the desired position command to the actuator at times the magnitude of the difference signal is less than or equal to the predetermined value, two dividers, two multipliers, an adder and normalizer for providing a new position command between the past command and the desired position command at times the magnitude of the difference signal exceeds the predetermined value.
    Type: Grant
    Filed: October 5, 1982
    Date of Patent: July 31, 1984
    Assignee: Westinghouse Electric Corp.
    Inventors: R. James Bennett, Robert A. Phillips
  • Patent number: 4456862
    Abstract: A method for augmenting a noise-adaptive predictive proportional navigation terminal guidance scheme. In a second order configuration with noise adaptive varying gain parameters calculated as a function of time-to-go, this system implements an optimal control law to augment proportional navigation with a missile acceleration feedback term and a navigation ratio to account for first order autopilot time lag. This configuration results in nearly optimal miss distance behavior, with sensitivity to unmodeled errors being substantially less than that in modern guidance systems. The system is particularly useful for high altitude, minimally maneuvering targets.
    Type: Grant
    Filed: September 22, 1982
    Date of Patent: June 26, 1984
    Assignee: General Dynamics, Pomona Division
    Inventor: William R. Yueh
  • Patent number: 4443853
    Abstract: An electrically controlled (16) mechanical actuator (13) is driven by optically generated (23) electrical power through an optically controlled (28) switch (26) in an electrically isolated module (20). Optical transducers (54, 62, 70) and feedback (29), as well as optical inputs (40, 89, etc.) to electrical signal processing equipment (46, 47, 49) in an electrically isolated module (22) dictate the electrical control (28). A helicopter flight control system is wholly digital, with solar remote power and optical intercommunication.
    Type: Grant
    Filed: April 20, 1983
    Date of Patent: April 17, 1984
    Assignee: United Technologies Corporation
    Inventors: Joseph R. Maciolek, Edmond D. Diamond
  • Patent number: 4426607
    Abstract: In a servoactuator system for an aircraft, a strapdown series servoactuator having an external linkage assembly is coupled between the pilot's control stick and a control surface member. The external linkage assembly includes a differential link and servo link having specially tapered stop surfaces adapted to be varied in dimensions to accommodate a wide variety of installations, which stop surfaces cooperate with fixed stops on the servoactuator housing whereby to provide a variety of pilot authority limits and series servo authority limits depending upon particular installation requirements.
    Type: Grant
    Filed: March 12, 1982
    Date of Patent: January 17, 1984
    Assignee: Sperry Corporation
    Inventors: Homer D. Black, Charles R. Stribley
  • Patent number: 4345195
    Abstract: Strapdown, multifunction actuator apparatus comprising one or two integral units adapted for installation in an aircraft, particularly a helicopter, and coupled between the pilot's control stick linkage and the aircraft control surface (or surface servo boost) linkage to perform the functions of series actuation, trim actuation, artificial feel, control position sensing, and control authority limits. The apparatus includes a series actuator installed in the vehicle and connected to the vehicle control linkages in the conventional parallel actuator manner; that is, it is secured directly or strapped down to the airframe and therefore greatly simplifies control system installation and reduces problems such as those associated with control rod vibration resonances normally encountered with conventional integral-with-linkage series actuator installations.
    Type: Grant
    Filed: August 8, 1980
    Date of Patent: August 17, 1982
    Assignee: Sperry Corporation
    Inventors: Carl D. Griffith, Kenneth L. Oliver
  • Patent number: 4337427
    Abstract: In a closed loop servo system in which the input signal is inaccessible and not available for measurement, but the error signal and output signal are both accessible and measurable, a filter configuration is provided which can be inserted into the error signal path of the system to reduce the undesirable effects of noise or other unwanted signals without appreciably affecting the closed loop dynamics of the overall system. In the generalized system a filter having the characteristics g(s) in LaPlace notation is inserted into the error signal path of the system to filter selected components of the error signal. A second filter having the characteristics h(s) which satisfies the equation g(s)+h(s)=1, is coupled between the output signal and the output of the filter having the characteristics g(s).
    Type: Grant
    Filed: December 22, 1980
    Date of Patent: June 29, 1982
    Assignee: General Dynamics, Pomona Division
    Inventor: Inge Maudal
  • Patent number: 4326685
    Abstract: A sun-sensing guidance system (10) for high-altitude aircraft (A) characterized by a disk-shaped body (14) mounted for rotation aboard the aicraft in exposed relation to solar radiation and having a plurality of mutually isolated chambers (28a, 28b, 32a, and 32b); each chamber of the plurality being characterized by an opening having a photosensor (34a, 34b, 36a, and 36b) disposed therein and arranged in facing relation with the opening for receiving incident solar radiation and responsively providing a voltage output, said photosensors being connected in paired relation through a bridge circuit (38) for providing heading error signals in response to detected imbalances in intensities of solar radiation incident on the photosensors of either pair of photosensors until a nulled relationship is achieved for the disk (14) to the source of radiation.
    Type: Grant
    Filed: March 12, 1980
    Date of Patent: April 27, 1982
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
    Inventor: Robert D. Reed
  • Patent number: 4196473
    Abstract: An instrument for determining and measuring the "X" and "Y" coordinate dinces a moving vehicle is located from a predetermined reference point at any given instant is disclosed as incorporating a tensioned range measuring wire, an angle sighting arm through which said tensioned range wire operates, range and angle potentiometers effectively connected to said tensioned range wire and angle sighting arm for constantly producing a pair of analog signals that are proportional to range and angular distances to said moving vehicle, respectively. A computer automatically computes the instantaneous "X" and "Y" coordinates of said vehicle with respect to the aforesaid predetermined known reference point from said pair of analog signals. An important and unique brake sub-combination permits the instrument and vehicle whose coordinates are being measured to be held in combined static equilibrium when they are not in use.
    Type: Grant
    Filed: September 18, 1978
    Date of Patent: April 1, 1980
    Assignee: The United States of America as represented by the Secretary of the Navy
    Inventor: Francisco Chea
  • Patent number: 4158196
    Abstract: The system provides a direct electrical interface between the electrical activity that may be self-induced in the human nervous system and the electrical activity in devices such as computers or calculators. Either one-way or two-way communication and/or control may be provided. For man-to-machine (efferent) communication bioelectric activity is monitored with electrodes and the action potentials which are self-generated are converted into digital signals preferably in the form of binary signals which may be interpreted by digital computers, micro-processors or other logic systems. For machine-to-man (afferent) communication binary signals in the form of binary ones or zeros are converted to action potentials. Depending upon the particular application, different codes are used to give specific meanings to specific patterns of bioelectric activity that the operator generates and specific patterns of electric stimulation that the operator receives.
    Type: Grant
    Filed: April 11, 1977
    Date of Patent: June 12, 1979
    Inventor: George E. Crawford, Jr.
  • Patent number: 4119900
    Abstract: The present method and system for the automatic orientation and control of a robot in a space or on a surface to be worked by the robot, for example an area to be vacuum-cleaned or a lawn to be mowed, employs a plurality of distance measuring devices, which continuously and repeatedly measure distances from the robot to points or small surface areas defining the surface to be worked. Electro-optical distance measuring devices are effective in a far range. Electro-acoustical distance measuring devices are effective in a close range. Electro and/or mechanical means are effective in a contact range. The distance measuring devices continuously ascertain scalar values which by means of data processing are transformed into digital control signals for the drive means and for the tools carried by the robot, whereby the robot plans its own driving and working strategies as the result of said continuous distance measurements.
    Type: Grant
    Filed: June 16, 1976
    Date of Patent: October 10, 1978
    Assignee: ITO Patent-AG
    Inventor: Walter Kremnitz
  • Patent number: 4092716
    Abstract: A method and device are provided for displaying the effect of control action in real time by simultaneously applying the control action both to the system to be controlled and a computer model of the system. The effect of the control action on the model is displayed to the operator in a manner which dynamically decouples the display to the operator in a manner which dynamically decouples the display from the actual system's response over some suitable frequency range, thereby enhancing the stability and performance of the control system's operation. The method and device are described in conjunction with a preferred embodiment of an aircraft gun fire control system and variation of that system. A computer model or pseudo aircraft, termed a command aircraft, is programmed into a computer carried by an actual aircraft. In addition to providing conventional control information to the actual aircraft, the control actions of the pilot "fly" the command aircraft.
    Type: Grant
    Filed: July 11, 1975
    Date of Patent: May 30, 1978
    Assignee: McDonnell Douglas Corporation
    Inventors: Robert L. Berg, William J. Murphy
  • Patent number: 4056732
    Abstract: The unregulated AC electrical power provided by an engine driven alternator to an airborne electronic engine control system which controls the performance of a gas turbine engine, is rectified to provide unregulated DC voltage signals for system electrical power. The system provides position control of a plurality of controlled surfaces within the engine through a plurality of digital effector servo actuators, each of which includes a mechanical assembly for providing displacement of the surface in each of two directions in response to a magnetic field provided by a respective one of two oppositely polarized solenoids disposed within the actuator.
    Type: Grant
    Filed: August 24, 1976
    Date of Patent: November 1, 1977
    Assignee: United Technologies Corporation
    Inventor: Anthony Newman Martin
  • Patent number: 4042867
    Abstract: Apparatus for remotely adjusting reference indicia of display instruments such as flight instruments wherein a knob affixed to the shaft of a d.c. generator, remotely disposed from the flight instrument produces a d.c. signal, the magnitude and polarity of which are dependent on the speed and direction, respectively, of rotation of the knob. The d.c. signal is coupled to a d.c. motor mechanically connected to said flight instrument reference indicia and adjusts the same accordingly. The apparatus further includes circuitry, electrically connected between the d.c. generator and the d.c. motor for producing compensating voltages equal to the start-up voltages of the d.c. motor, which when added to the d.c. signal insure a continuous response by the d.c. motor to the d.c. signal, and also for isolating the output impedance of the d.c. generator from the d.c. motor.
    Type: Grant
    Filed: June 30, 1975
    Date of Patent: August 16, 1977
    Assignee: Sperry Rand Corporation
    Inventors: Richard Earl Schaffer, Paul Allen Rauschelbach
  • Patent number: 4039165
    Abstract: The circuit derives a rate signal from an a.c. signal proportional to attitude displacement provided, for example, from the synchro pickoff of a vertical gyroscope or an inertial navigation system, the pickoff receiving power from the aircraft a.c. power supply. The a.c. attitude signal is passed through a first bandpass filter tuned to the frequency of the power supply. The a.c. power supply signal is passed through a second bandpass filter identical to the first whose output is used as the reference signal for first and second identical demodulation circuits which include first and second matched low pass filters respectively. The filtered a.c. attitude signal is applied to the first demodulator circuit and the filtered power supply signal is applied to the second. The output of the first demodulator circuit is applied to a line voltage compensator and the output from the second demodulator circuit is applied to a d.c.
    Type: Grant
    Filed: June 4, 1976
    Date of Patent: August 2, 1977
    Assignee: Sperry Rand Corporation
    Inventor: Henry E. Hofferber
  • Patent number: 4033525
    Abstract: A feedback PDM encoder and method is presented which permits utilization of neumatic pulse duration modulation (PDM) actuators with potentiometer position pickoffs in a digital autopilot loop. The actuator is directly driven by a signal derived in the digital autopilot which is in the pulse duration modulation (PDM) format. This signal is derived within the autopilot digital computer using conventional digital techniques. Analog feedback from the potentiometer which indicates angular excursion of the actuator is formatted into a PDM format. This method yields all signals necessary to operate the actuator in a closed loop missile control system.
    Type: Grant
    Filed: December 8, 1975
    Date of Patent: July 5, 1977
    Assignee: The United States of America as represented by the Secretary of the Army
    Inventors: John P. Leonard, Robert E. Yates
  • Patent number: 4030011
    Abstract: A control system exhibiting more than one system response characteristic depending on input signal parameters, and without requiring discrete switching of system components, is disclosed. At least one system input signal of varying frequency and amplitude is supplied to both high pass and low pass filters, the output of one of which is amplitude limited and additively combined with the output of the other filter to form a first intermediate control signal which is subtractively combined with the input signal to form a second intermediate control signal. The first and second intermediate control signals are passed through signal transfer elements having different signal transfer characteristics, and then combined to provide multimode response.
    Type: Grant
    Filed: March 24, 1975
    Date of Patent: June 14, 1977
    Assignee: Honeywell Inc.
    Inventors: Russell C. Hendrick, John C. Larson
  • Patent number: 3936715
    Abstract: A system for electrically actuating the pitch trim of an aircraft in both autopilot and manual modes includes a primary pitch servomotor coupled to a primary control surface and a pitch trim servomotor for actuating a trim control surface. In the autopilot mode, an electrical signal applied to the primary pitch servomotor by the autopilot is also applied to two channels of a trim controller providing complementary output signals applied to the pitch trim servomotor. Each channel of the trim controller includes a voltage translator for providing a single ended voltage applied to an integrator that generates an output varying with the time average of the electrical signal applied to the primary pitch servomotor. This time average signal as generated in each channel is chopped into an alternating current signal for driving an output stage. The chopping duty cycle of each channel is varied in accordance with the absolute value of a time average of the electrical signal applied to the primary pitch servomotor.
    Type: Grant
    Filed: August 9, 1974
    Date of Patent: February 3, 1976
    Assignee: Edo-Aire Mitchell Industries, Inc.
    Inventors: John M. Nixon, James R. Younkin