The electric wheelchair includes a battery pack (A), a right drive motor (B), a left drive motor (C), and a control circuit for controlling the amount of power supplied from the battery to the left and right control motors A speed potentiometer (24) and a direction potentiometer (26) are connected with a joystick (22) for producing a selected vehicle speed signal and a selected vehicle direction signal, respectively A right speed control circuit (E) and a left speed control circuit (F) receive the selected vehicle speed and direction signals and control the right and left motors in accordance with them Each speed control circuit includes a reference signal circuit (90) which receives the selected vehicle speed and direction signals and produces a reference signal whose magnitude varies with the speed selected for its motor The voltage and current across the armature of the motor are detected as measures of the motors actual speed A comparing circuit (92) compares the actual speed as determined by the armature voltage and current with the selected speed as denoted by their reference signal Specifically, it subtractively combines the armature voltage and the reference signal to produce a first difference signal Further, it subtractively combines the first difference signal with the armature current signal to produce a speed error reference signal The speed error reference signal controls a variable power regulator (94) which varies the amount of power supplied to the motor in a manner which tends to cause the actual and selected speeds to match

Electric wheelchair with improved control circuit

The placement of fully available prime movers having a DC output at a location inside or adjacent to an inverter-based intermittently available renewable energy site is disclosed. The fully available prime movers add reliability to an unreliable energy asset that is reaching its maximum penetration within the grid due to its unpredictability and the requirement for additional spinning reserves in other parts of the grid. The present invention can provide a portion or all of the power to an intermittently available renewable power generating facility so that the power output to the power grid is dispatchable power. In particular, a method and means are disclosed to utilize high-efficiency engines operated on various fuels some of which may be non-fossil fuels to maintain a constant power output from an otherwise intermittent power generating facility.

Dispatchable power from a renewable energy facility

An induction motor drive apparatus of the type having a speed detector for detecting the rotational speed of an induction motor, speed command device for producing a command speed, and an error amplifier for amplifying a difference between the rotational speed of the induction motor and the command speed, the induction motor being driven by so controlling the amplitude of the primary current as to vary the amplitude of the secondary current in accordance with the difference between the rotational and command speeds. Included are two-phase sinusoidal wave generating device for generating two sinusoidal signals displaced in phase from one another by π/2 and whose amplitudes conform to the output of the error amplifier, primary load current arithmetic device for computing a primary load current by employing the output of the error amplifier and the output of the two-phase sinusoidal wave generating means, and primary current arithmetic means for computing a two-phase primary current command by adding the primary load current to the output of the two-phase sinusoidal wave generating device, which output serves as an excitation current. The induction motor is driven by the primary current command having an excitation current component and a primary load current component the amplitudes of which vary in accordance with the difference between the rotational speed of the induction motor and the command speed.

Induction motor drive apparatus

Large work vehicles include hydraulic implement control systems having an hydraulic pump being driven by an internal combustion engine. The subject invention provides a method and apparatus for controlling such an hydraulic system to control engine lug while the hydraulic system is operating. The apparatus includes one or more sensors for producing parameter signals in response to the level of one or more hydraulic system operating parameters. A control receives the parameter signals and responsively produces a supplemental control signal which is used to control engine lug.

Hydraulic power control system

Microprocessor controlled automatic power control for adjusting the engine power setting in an engine-transmission power train in which the transmission drive reduction is variable in ratio, by step change or continuously so, such as for use in farm tractors. The microprocessor control monitors the position of this automatically moving lever and the desired transmission output speed to keep the setting adjusted so that engine power is set, within a deadband, to maintain a desired engine speed preferably resulting in minimum fuel consumption or in maintaining constant transmission output speed. Preferably, the microprocessor has a higher priority primary function of also automatically adjusting the transmission drive reduction ratio, for the same purpose but with higher sensitivity. The power control lever is specifically designed to automatically return the power setting to manual control as soon as the operator grabs the handle.

Automatic power control for variable power train

An improved apparatus is provided to control the operation of a plurality of hydrostatic transmissions which are advantageously utilized to drive the tracks of a vehicle. This apparatus includes a signal generator which provides an electrical ratio command signal which is variable to correspond to any one of a plurality of displacements and output speeds of a pair of hydrostatic transmissions. Right and left steering command signal generators are selectively operable to provide electrical steering command signals which effect operation of actuator assemblies to vary the output speed of one of the hydrostatic transmissions relative to the other hydrostatic transmission to turn the vehicle. A straight tracking control apparatus includes a pair of speed sensing units which are effective to provide electrical speed signals which vary in value as a function of variations in the output speed of an associated hydrostatic transmission. During movement of the vehicle along a straight path, the electrical speed signals are compared and utilized to effect activation of one or more of the actuator assemblies if the output speed of one of the transmissions is different from the output speed of the other transmission. Upon actuation of the steering controls, the straight tracking apparatus is rendered ineffective so that the vehicle can be turned. Anti-stall circuitry is provided to prevent overloading of the engine.

Electrical hydrostatic transmission control system

A control for a plurality of drives each of which includes a driven load associated therewith includes a reference generator for generating a pulse train wherein each pulse is indicative of a desired incremental movement of the load and the frequency of the pulses is indicative of a desired velocity of the load, a plurality of sensing means each of which is associated with one of the drives for generating a feedback pulse train wherein each pulse is indicative of an actual incremental movement of its associated load and the frequency of the pulses is indicative of the actual velocity of its associated load and a plurality of digital summers each of which is associated with one of the drives for summing pulses of the reference pulse train and the feedback pulse train and establishing a positional error signal. A velocity control means is provided responsive to the error signal for driving the associated load at substantially the desired velocity. The control further includes a plurality of second sensing means each of which is associated with one of the loads for sensing an actual position of the associated load and establishing a signal indicative of the actual position of the associated load, synchronizing means responsive to each of the actual position signals for determining the relative position of one of the loads relative to another of the loads and phase jogging means responsive to the synchronizing means for incrementally shifting the phase of one of the loads relative to another of the loads to bring the one load into phase with the other load. The phase jogging means may also be operated independently of the synchronizing means to establish a phase relationship which is not necessarily limited to an in-phase relationship between the one and the other associated load. Thus, the present control system is operable to velocity lock a plurality of drives together and hold the driven members of the drives in a predetermined variable phase relationship.

Controlled velocity drive

A control for a controlled-velocity drive having a driven member and an electromagnetic coupling having a winding the energization of which controls the angular velocity of the driven member. A triggerable semiconductor current switching device is adapted to be connected between a source of AC power and the winding for controlling the energization thereof. Three feedback circuits provide degenerative feedback signals respectively varying according to the driven member angular velocity, the current in the winding and the rate of change of the current. Means is provided for producing a reference voltage proportional to a preselected angular velocity of the driven member. Circuitry is responsive to the reference voltage and to the three feedback signals for causing triggering of the current switching device at varying phase angles of the AC power to drive the driven member substantially at said preselected angular velocity. This circuitry is also operational for causing triggering of the switching device at a substantially constant phase angle of the AC power to cause conduction of the switching device when the AC power voltage and the voltage across the winding are inverted so that current in the winding decays rapidly when energization thereof is rapidly reduced. Various optional control functions are also provided which may be connected by jumper leads.

Controlled-velocity drive control

In a motor control system in which an induction motor is driven by an inverter and the motor tends to resonate, the resonant frequency of the motor and the extent of its damping are adjusted to desirable amounts by a local feedback circuit. An output signal of the local feedback circuit is algebraically added to a speed command voltage for the motor control system. A sum signal thus produced is connected to the input of the inverter to control the motor speed. The sum signal is also employed as one of two input signals to the local feedback circuit, the second input signal being proportional to the speed of the rotor of the motor and obtained from a sensor connected with the rotor shaft. The two input signals to the local feedback circuit are subtracted and their difference signal is processed through a lag circuit and a filter network to produce the output signal of the local feedback circuit. When the inverter and motor are thus stabilized by the local feedback circuit just described, it is much easier to stabilize a larger speed-control feedback loop in which the inverter and motor may be employed.

Gerald F. O'callaghan

Papers

Electrical hydrostatic transmission control system

Controlled velocity drive

Controlled-velocity drive control

Stabilizing system for an inverter-driven induction motor

Speed control apparatus with eddy current clutch and brake means