Abstract: A seam-tracking apparatus for a welding system has a welding arm which directs an energy beam toward a seam. The seam-tracking apparatus includes an eddy current sensor formed by an array of eddy current elements, each producing a respective electrical signal when positioned adjacent to the seam to be tracked. An eddy current signal processor receives each respective electrical signal so as to generate position data indicative of the location of the seam. A controller is responsive to the position data so as to align the eddy current sensor and the welding arm over the seam so that the energy beam continuously impinges on the seam, as the welding arm advances along the seam. The eddy current sensor may be flexible, in which case the seam-tracking apparatus can track a seam between workpieces having curved surfaces.

Abstract: A controlled EDM apparatus comprises at least one electrode mounted in a base, a driver for positioning the base, a system for providing electrical energy to the electrode, a monitor for measuring the electrical discharge frequency of the electrode, and a controller responsive to the monitor for controlling either the driver or the energy providing system. The apparatus operates by measuring the electrical discharge frequency of the electrode and controlling at least the duration of machining in accordance with the frequency measured.

Abstract: A torque feedback system is employed in a universal field-oriented (UFO) controller to tune a torque-producing current command and a slip frequency command in order to achieve robust torque control of an induction machine even in the event of current regulator errors and during transitions between pulse width modulated (PWM) and square wave modes of operation.

Abstract: This real time adaptive control and method of controlling a spot welding process compensates for electrode wear, oxidized surfaces, fit up variations and machine variations. Workpiece thermal growth is the measurement discriminant and the welding machine heat command is the control input. The control utilizes a least squares estimator to monitor the process and workpiece displacement, a precompensator to shape a desired displacement trajectory command, and a model reference control with a Smith-predictor to compensate for time delays and a proportional-integral-derivative compensator. The model reference control has a mathematical model of the spot welding process and calculates an estimated displacement using a predicated process gain and bias calculated by the estimator. The estimated displacement is compared to the precompensator displacement trajectory and an error is generated which regulates the heat command through the PID compensator.

Abstract: To control the welding current in a resistance spot welding system, a current measurement sensor is used with a current feedback control to vary the firing angle of power devices in the primary side of the power supply. The closed-loop feedback control assures the desired current is applied independent of variations in the resistance of the welding equipment and primary line voltage variations. In the current feedback control, the commanded current, proportional error, integral error and line voltage offset are summed to derive the firing angle signal, and the power supply is adjusted until actual current equals the desired current.

Abstract: A real time steering capability is provided to permit robot motion to be modified continuously in three dimensions as the robot is moving along a taught path. An arc welding robot or other taught path robot has a sensor located on the robot arm to sense the position of a desired path. The tracking control provides real time steering commands to the standard robot taught path and are calculated based on maintaining a constant, preprogrammed velocity along the desired path and coordination with the taught path. Offsets to the robot taught path are computed in a manner that allows the robot to smoothly follow the actual path as measured by the look ahead path sensor. The offsets are determined as separate x, y, z and twist integrations for the end effector and represent the total deviations from the robot taught path.

Abstract: A flowmeter of the fluid oscillator type having a fluid jet which oscillates at a frequency indicative of flow rate. A linear flow rate vs. frequency output characteristic is obtained by use of a fluid accelerating means in the form of a two-dimensional sharp edge orifice. The orifice has an aspect ratio selected to give a constant coefficient of discharge throughout an extended flow range including laminar and turbulent flow conditions.