Abstract: A motor controller detects the speed at which a driven member is travelling when it enters a slow-down region of a material handling system. Using this speed and a deceleration rate, the motor controller determines a required slow-down distance to reach a desired slow speed. A traverse distance is determined as a difference between the length of the slow-down region the slow-down distance. The traverse distance extends for a first portion of the slow-down region and the slow-down distance extends for the second portion of the slow-down region. While the driven member is located within the traverse distance, the driven member may continue operating at the speed at which it entered the slow down region. When the driven member reaches the slow-down distance, the motor controller begins decelerating the driven member.

Abstract: A motor drive receives a position feedback signal from an encoder operatively connected to the motor. The motor drive executes a speed regulator module on a first periodic interval to achieve desired operation of the motor, and the motor drive executes an additional module at a second periodic interval, occurring more frequently than the first periodic interval, to increase the resolution of the position feedback. The position feedback signal is provided as or converted to counts. The motor drive maintains a first counter with a running total of each count received as well as a second counter which generates a higher resolution value than the first counter. During each second periodic interval the motor drive increments the high-resolution counter by the number of actual counts detected within the corresponding first periodic interval. This high-resolution counter is used by the speed regulator to obtain desired operation of the motor.

Abstract: A method and system to prevent unexpected operation of a motor when the voltage level on a DC bus drops is disclosed. The voltage level on the DC bus is monitored during a run command. When a run is commanded, the processor executes a control routine to determine a desired amplitude and frequency for the output voltage required to control the motor connected to the motor drive. If the desired frequency of the output voltage exceeds a maximum frequency for the measured voltage on the DC bus, as established by parameters stored in the motor drive, the motor drive limits the output frequency to the maximum frequency for the corresponding measured voltage. The motor drive continually monitors the measured voltage present on the DC bus and further reduces the maximum output frequency allowed during the run if the present value of the measured voltage drops below a previously measured value.

Abstract: A method and system for reducing rollback in a counterbalancing system as a holding brake is released is disclosed. A limited amount of movement of a drive shaft is present in the holding brake. A motor drive provides current to the motor with the holding brake set such that a torque is applied at the drive shaft. The current is controlled to generate torque in both directions. The limited amount of movement in the brake may be used to determine a direction and magnitude of torque required to support a mechanical load being applied to the motor. The motor drive then provides a current to generate the necessary torque required to support the load prior to releasing the holding brake.

Abstract: A system and method for determining the load in a material handling system is disclosed. The load weight detection system measures torque at four operating conditions both at constant speed and during acceleration. The level of torque generated by the motor under each of these operating conditions is stored in the motor drive. The motor drive also receives a signal corresponding to the speed of the hoist motor. Based on the measured torque, as well as the expected torque at no load and at rated load for the measured speed, the motor drive then determines the load present on the hoist. In some systems, two or more hoists are required to operate in tandem to lift a load. Each motor drive determines the weight of the load supported by its respective hoist motor and determines a total weight of the load based on the weights determined by each motor drive.

Abstract: A control system for a bucket hoist includes a two-axis master switch configured to generate a first and a second command signal responsive to motion along each axis. Each command signal is provided to one of a pair of motor controllers configured to control one of a pair of motors. The two motors are controlled to raise/lower and open/close the load handling member. When the two-axis master switch is moved to the close position, the closing motor controller is commanded to control its respective motor to begin closing the load handling member. The holding motor controller is configured to generate a current to its respective motor to generate torque at a predefined level. The predefined level of torque is selected such that the load handling member lowers into the material in which it is digging as it is being closed.

Abstract: A system and method for determining the load present in a material handling system is disclosed. A commissioning routine executing on a motor drive controls operation of a hoisting motor with a known load present. The commissioning routine stores values of current provided to the motor or torque generated by the motor at various operating speeds in memory on the motor drive. During subsequent runs of the motor drive, the value of the current/torque is monitored as a function of the speed of the motor and compared to the stored values. The resulting value of the load may be monitored and action taken if the value of the load exceeds the rated capacity of the material handling system. Optionally, the measured load may be displayed to an operator.

Abstract: A controller for mobile hydraulic equipment includes a radio receiver, hydraulic controller, and display unit. The controller further includes terminals configurable to function as a combination of analog or digital inputs or outputs according to the system requirements. A user interface included on the controller permits an operator to select a desired function for each terminal and to configure the controller according to the application requirements.

Abstract: A system for determining the angular position of a synchronous motor includes an encoder with a friction wheel engaging a rotating surface of the motor. The friction wheel is spun by the rotation of the motor, and the encoder generates a signal corresponding to the angular position of the friction wheel. An independent, sensor is provided to generate a pulse once per revolution of the motor. The independent sensor detects the presence of a target on the rotating surface of the motor and generates the pulse when the target is proximate to the sensor. A controller receives the signal corresponding to the angular position of the friction wheel as well as the pulse generated by the independent sensor to determine the angular position of the motor. The controller compensates the angular position of the motor each time the pulse is generated, correcting accumulated position error.

Abstract: A system and method for determining the holding torque of a brake in a material handling system is disclosed. The material handling system may include a bridge, a trolley, and a hoist, each driven along a different axis by a motor. A brake is operatively coupled to the motor to prevent unwanted motion of the motor. A motor controller is coupled to each motor which controls operation of the motor and its corresponding brake. The motor controller generates a torque command to the motor while keeping the brake set. The initial torque command is less than the holding torque of the brake. The torque command is incremented until motion is detected on the motor. The torque value when motion is detected is stored in the motor controller and displayed to an operator.

Abstract: A variable speed power converter controls the speed of a load in a material handling system as a function of the torque required to move the load. While the power converter is running, the torque being produced in the motor is determined. The power converter then determines the maximum rotational speed of the motor as a function of the torque currently being produced and of the torque-speed curve of the motor. The power converter then commands the motor to rotate at this maximum rotational speed. The power converter periodically monitors the torque being produced and adjusts the maximum rotational speed of the motor throughout the run.

Abstract: A controller for mobile hydraulic equipment includes a radio receiver, hydraulic controller, and display unit. The controller further includes terminals configurable to function as a combination of analog or digital inputs or outputs according to the system requirements. A user interface included on the controller permits an operator to select a desired function for each terminal and to configure the controller according to the application requirements.

Abstract: A controller for mobile hydraulic equipment includes a radio receiver, hydraulic controller, and display unit. The controller further includes terminals configurable to function as a combination of analog or digital inputs or outputs according to the system requirements. A user interface included on the controller permits an operator to select a desired function for each terminal and to configure the controller according to the application requirements.

Abstract: An electronic limit switch software module is programmed into a controller for a hoist system. The electronic limit switch determines the rotations of a motor to keep track of the location of the load. Arbitrary stop and slow down locations may be input into the system so that the system can determine when to stop and slow down the load.

Abstract: A power converter includes at least two power conversion sections operating in parallel. The power converter receives a variable input power and generates an AC output voltage. When the power source is generating enough power to supply a DC voltage to the power converter greater than or equal to the peak magnitude of the desired AC voltage output, each power conversion section operates in parallel, converting the DC voltage to the desired AC voltage output. When the power generated by the variable power source results in a DC voltage having a magnitude less than the peak magnitude of the desired AC voltage output, the power conversion sections operate in series. One power conversion section operates as a boost converter to boost the DC voltage level to a suitable level for the second power conversion section, which generates the desired AC output voltage.

Abstract: A DC motor control device calculates motor speed using determinations of motor field flux and armature voltage in the motor. The device includes a control module having one or more control inputs and one or more control outputs. At least one control input is configured to receive data representing field current measured in the DC motor. The control module includes flux curve logic that is responsive to measurements of motor field current to calculate a field flux in the motor. The flux curve logic uses a flux curve stored in the control module, the flux curve representing a functional relationship between field current and field flux in the motor. The flux curve is defined by a plurality of flux curve data points corresponding to a plurality of motor field currents within a lower current range and within an upper current range. The flux curve is further defined by at least a first flux curve line positioned within the lower current range and a second flux curve line positioned within the upper current range.

Abstract: Two incremental shaft encoders are mounted on the two extreme ends of a mechanical drive train. The encoders generate data which is representative of the rotational speed of the drive train component proximate to where the encoder is mounted. The data from the encoders is communicated to a logic unit associated with operation of the drive train, such as a variable frequency motor drive (VFD). Software in the logic unit monitors and compares the speed of both encoders. An encoder resolution setting and a gear ratio are entered into the software parameters. If a difference in speeds (as monitored and indicated by the encoders) is greater than a preset value for a period longer than a preset time period, the logic unit displays an error message and a programmed action (such as motor shutdown and load braking) is executed.

Abstract: Included herein is a system and method for controlling a velocity vector of an overhead crane. A motor is attached to the crane and is positioned to move the overhead crane and has an output vector including a rotational direction and a rotational speed. A variable frequency drive is positioned to transfer voltage and current at a frequency to the motor. A processing unit converts the output vector to an amount of voltage and current at a given frequency and can instruct the variable frequency drive to send a frequency to the motor at a frequency substantially equal to the frequency at which the motor is presently rotating. This creates a speed match for the motor reducing spikes during operation of the motor and substantially eliminates open circuit decay. A hydraulic brake operates in connection with the processing unit and the variable frequency drive to slow the crane without driving the motor into the brake.

Abstract: A hoist synchronization apparatus and method using a master controller operating software that provides a pulse reference to a slave controller. The slave commands its motor to rotate at the speed conveyed by that pulse reference. The slave controller monitors the pulse feedback from both the master encoder and the slave's encoder and compensates for any position error by adjusting its motor output speed. In addition, the slave controller includes the capability to automatically resynchronize the hoists. Resynchronization is accomplished by storing position error generated when either the master or the slave is run independently and correcting for the error when both units are operated at a later time.

Abstract: A dual hoist bucket crane controller for operating a closing motor and a holding motor using a close inverter adapted to control the closing motor and a hold inverter adapted to control the holding motor where the hold inverter and the close inverter are internally controlled and operate independently from the other drive. Also covered is a dual hoist bucket crane controller for operating a closing motor and a holding motor using a dual axis master switch adapted to provide a close inverter input signal to the close inverter and a hold inverter input signal to the hold inverter.