Westinghouse Electric Corporation

William R Caputo

Alan L Husson

John J De Lorenzi

Masami Nomura

Jitendra K Trivedi

Albert J Pisatowski

Kenneth K Lee

A method and apparatus for smoothly stopping an elevator car at a target floor in an elevator system which utilizes a speed pattern to control car speed via a speed feedback control loop. When the elevator car reaches a predetermined slowdown point relative to a target floor, the speed pattern is changed towards a predetermined minimum non-zero value, with the non-zero value being selected to insure that the car will reach the floor in the event of error in the arrangement used to change the value of the speed pattern. The speed pattern value is then independently forced to a value indicative of zero car speed in response to a detector which detects the actual presence of the elevator car as it reaches a predetermined small dimension from the target floor, to stop the car at floor level, before a holding brake is applied.

Method and apparatus for smoothly stopping an elevator car at a target

A method for providing a load compensation signal for the drive motor control loop of a traction elevator system which includes an elevator car, a counterweight, and a drive which includes a drive motor, brake, and traction drive sheave. The brake is mounted to provide an indication of the direction of unbalanced brake torque, with the method including the step of detecting unbalanced brake torque when the elevator car is stationary. A car load compensation signal is provided in response to the detecting step, with the compensation signal transferring the unbalanced torque from the brake to the drive motor, building up the motor current to provide motor torque sufficient to hold the car stationary while the brake torque is reduced to zero. The method then continues by using the motor current to provide car loading signals for use by the supervisory control portion of the elevator system.

Method for providing a load compensation signal for a traction elevator

A method and apparatus for providing a load compensation signal for the drive motor control loop of a traction elevator system which includes an elevator car having a load responsive platform and a counterweight. The load compensation signal transfers unbalanced torque from the system brake to the drive motor at the start of the run, to provide smooth starts. The load compensation signal is heavily filtered to provide a response time which will follow changes in car loading but too slow to affect car dynamics. Thus, the load compensation signal is continuously connected to the motor control loop, eliminating switches and memories, and enabling the compensation signal to directly aid car landing. Non-linearities in the load responsive platform are partially compensated for by three initial adjustments, and a fourth adjustment is provided for periodically offsetting changes due to ageing of platform isolation materials. The load compensation signal may be added directly to the motor control loop, or further processed to account for hoist cable weight compensation error at the location of the elevator car.

Method and apparatus for providing a load compensation signal for a

Transportation apparatus, such as escalators and moving walks, having an electrically released, magnetically set brake, and a servo loop for regulating the brake coil current. Brake voltage and brake current feedback are both used in the regulation of the brake current, with the values of the voltage and current feedback being selected to cause electromagnetic flux produced by the brake coil current to substantially cancel the magnetic flux produced by permanent magnets over the operating temperature range of the brake. In a preferred embodiment of the invention, the brake current is pulsed continuously while the transportation apparatus is operated, to prevent transient excursions of the brake current from initiating and maintaining partial setting of the brake.

Transportation apparatus

A PWM inverter in which the maximum three-phase RMS pole-to-pole output voltage is increased, to more efficiently utilize a fixed DC power supply, by generating substantially sinusoidal changing pole voltages having no values within predetermined zones adjacent to each power supply limit, and by switching each pole voltage to a power supply limit for a predetermined number of electrical degrees during each half cycle, resulting in step changes in the pole voltage waveforms from the substantially sinusoidal changing waveform to a fixed power supply limit.

PWM inverter

Transportation apparatus, such as escalators and moving walks, having controlled stopping characteristics. Deceleration is directly regulated via a deceleration servo loop which provides a current reference signal for an inner current loop. Brake current limiting prior to the controlled stop, as well as mechanically limiting the maximum brake gap, results in faster transient response, and a more linear braking torque versus brake current characteristics. Multiple drive units operate from a common deceleration reference signal, while having independent servo loops each operating from a 'local' deceleration signal.

An elevator system which generates a landing speed pattern having the advantages of both digital and analog based patterns, without the disadvantages of either, by generating a landing speed pattern which is a digital, i.e., absolute position, and analog composite. The absolute position of the elevator car in the landing zone of a target floor is detected at only a few points on each side of floor level, and an absolute pattern value is stored in memory for each such point. The stored speed pattern values are retrieved as the car arrives at each absolute position point and used for establishing the landing speed pattern, with the last such value being modified to provide a continuous pattern which smoothly blends with the next stored speed pattern value as the elevator car reaches the next absolute position point.

Elevator system

An angular accelerometer which generates a directly usable signal in stationary coils proportional to the instantaneous acceleration rate of a rotating element. Errors due to wobble, eccentricity and non-homogeneity of the rotating element are reduced by a symmetrical generation of flux which links the element, and a symmetrical detection of flux produced by current flow in the element.

Angular accelerometer

A friction driven tachogenerator having a friction drive wheel in contact with a movable member. The tachogenerator is compliantly and frictionlessly mounted, and at least one pressure roller is disposed in tangential, rolling contact with the friction drive wheel. The pressure roller biases the friction wheel against the movable member to provide a predetermined contact pressure between the friction wheel and movable member without applying a significant load to the shaft and bearings of the tachogenerator. The compliant and frictionless mounting of the tachogenerator is devoid of friction sources which can interfere with the sensing of velocity oscillations by the tachogenerator.

Tachogenerator

A feedback controlled elevator system including a speed pattern generator for providing a speed pattern signal responsive to desired speed. A limiting signal responsive to the absolute position of the elevator car is compared with the speed pattern signal, and the lesser of these two signals is compared with a velocity signal to determine speed error.

An elevator system which develops information relative to car location in the associated building from an extensible coded tape in the hoistway. The tape is tensioned and then fixed at predetermined locations such that predetermined positional relationships between the tape and the hoistway remain fixed, notwithstanding compression of the building and temperature induced dimensional changes of the tape.

An elevator system having an elevator car and a drive system for operating the elevator car. The drive system is forced to adaptively appear to have a desired transfer function in response to a speed pattern signal. In one embodiment, the speed pattern signal is developed by applying the ideal speed pattern, without lag compensation, to a function which provides a response in accordance with the reciprocal of the desired transfer function. In another embodiment, the speed pattern signal is the ideal speed pattern, with lag compensation, and the reciprocal of the desired transfer function is not required.

An elevator system including an elevator car, and control apparatus for controlling its speed, including a floor selector and a speed pattern generator. The speed pattern generator provides a running speed pattern, and a slowdown speed pattern. A smooth transfer from the running speed pattern to the slowdown speed pattern is achieved by the generation of first and second deceleration signals, and a transfer signal. When the floor selector issues a slowdown signal, the slowdown speed pattern is initiated and the first deceleration signal causes the running speed pattern to have a zero rate of change. First and second different relationships between the running speed pattern and the slowdown speed pattern then successively cause the issuance of the second deceleration signal and the transfer signal, with the second deceleration signal causing the running speed pattern to have a predetermined constant rate of change, less than that of the slowdown speed pattern, such that the patterns intersect. Pattern equality causes the issuance of the transfer signal, which initiates the substitution of the slowdown speed pattern for the running speed pattern.

An elevator system including a comparator which develops a control signal responsive to the actual versus the designed performance of the elevator car as it approaches a floor at which it is to stop. This control signal is used in a monitoring and protective arrangement which controls pre-opening of the doors before the elevator car stops at a floor, as well as providing additional protection relative to the operation of the elevator car after it has made an inaccurate landing, and back-up protection for any movement of the elevator car with its doors open.

An elevator system of the traction type having a direct current drive motor and a solid-state, dual-bridge converter power supply. Protective and monitoring apparatus reduce the probability of fuse blowing due to improper gating of a controlled rectifier device, and/or a power supply interruption, while enabling the system to override longer power supply interruptions without initiating shutdown in certain instances. The deceleration range of the elevator car is narrowed, when an orderly shutdown is required, by sensing predetermined parameters of the elevator system and logically selecting the value of a dynamic braking resistance in response thereto.

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Wyckoff, NJ, United States of America

William R Caputo