Abstract: An indirect speed sensor for an electric motor, such as an electric motor of the universal type, provides for a resistive element in series with the motor windings so that current pertubations that occur as a consequence of armature rotation are manifested as speed-dependent voltage signals across the resistive element. The voltage signals are amplified and filtered to remove frequency components above and below the expected signal spectrum and then provided to an analog-to-digital converter that converts the filtered analog signal to digital values that are stored in a memory. A stored-program controlled microprocessor analyzes the stored digital information by performing a fast Fourier transform to provide an equivalent amplitude spectrum. The maximum amplitude spectral component is then identified to determine the speed of the motor.

Abstract: A waveform synthesizer for generating single or poly-phase waveforms of selected wave shape and frequency for driving AC machinery including, for example, single or poly-phase induction, synchronous or other type motors or the like, includes a plurality of controllable power-switching device pairs for selectively switching power from an oppositely poled DC source to the corresponding power utilizing circuits of the driven device. The switching device pairs are controlled to provide switched pulses of selected widths, spacings, and repetition rates to generate the desired current waveform. The power-switching device pairs are selectively switched by a control circuit that includes a microprocessor-controlled memory that is divided into P addressable pages with each page including S sequentially accessible memory locations containing the switching device pairs control information necessary to synthesize the desired waveform.

Abstract: A waveform synthesizer for generating single or poly-phase waveforms of selected wave shape and frequency for driving AC machinery including, for example, single or poly-phase induction, synchronous or other type motors or the like, includes a plurality of controllable power-switching device pairs for selectively switching power from an oppositely poled DC source to the corresponding power utilizing circuits of the driven device. The swithching device pairs are controlled to provide switched pulses of selected widths, spacings, and repetition rates to generate the desired current waveform. The power switching device pairs are selectively switched by a control circuit that includes a microprocessor controlled memory that is divided into p addressable pages with each page including s sequentially accessible memory locations containing the switching device pairs control information necessary to synthesize the desired waveform.

Abstract: A method of fast charging batteries by means of precise analysis of the profile of the variation with time of a characteristic of the battery which is indicative of the variation in stored chemical energy as the battery is charged. The method specifically comprises analyzing the profile for the occurrence of a particular series of events preferably including one or more inflection points which precisely identify the point in time at which the application of a fast charge rate should be discontinued. Additional methods of analysis provide for termination or control of the charging current upon the occurrence of other events such as limiting values on time, voltage or voltage slope or a negative change in the level of stored energy.Apparatus for performing these methods comprises a suitable power supply and a microcomputer for analyzing the profile and controlling the power supply.

Abstract: A method and apparatus are presented for charging batteries at a high rate without damaging or reducing the life of the battery. The method comprises monitoring the level of energy stored in the battery, preferably by monitoring a particular battery characteristic. The variation of the characteristic with time is analyzed, preferably by measuring successive values of the characteristic, computing the slope and comparing successive slope values so as to identify inflection points and other significant events in the variation of the characteristic.Apparatus for performing these methods and for controlling the supply of energy is disclosed which comprises suitable power supply and a programed microcomputer for measuring successive values of the characteristic, performing the required computations, and controlling the supply of energy applied to the battery by the power supply.

Abstract: A microcomputer controlled power tool including a semiconductor control device connected to the motor, one or more sensors, and a microcomputer interfaced to a keyboard and digital display for monitoring and controlling various operating conditions and parameters of the power tool.

Abstract: A digital control system for electric motors in power tools of the portable or stationary type includes a microcomputer controlled speed regulator connected to the electric motor for maintaining a preselected speed of the motor substantially constant between no load and full load operation of the motor. The preselected speed is inputted to the microcomputer by means of a rotary switch or similar input switching arrangement. When the tool is just starting or the operator changes the speed switch, the microcomputer controls the speed of the motor to slowly approach the desired speed. The microcomputer is programmed to detect an overload condition and activate an alarm, and an impending kickback condition and stop the electric motor.

Abstract: An impending kickback condition is the operation of a power tool or machine tool system is sensed and used to control or eliminate the kickback. The ability to sense an impending kickback condition can be used in all categories of power driven tools. The change in force applied to the power driven tool or other implement is monitored by measuring the rate of change of speed of the tool or implement, and if the speed is decreasing, the rate of change of speed is compared with a threshold value which may be either preset or variable. If this threshold value is exceeded, an output control signal is generated which inhibits the coupling of power to the tool or other implement and/or applies a brake to stop the tool or implement. In order for power to once again be coupled from the motive power source to the shaft, the start switch must be opened and then reclosed or some other signal provided by the operator or another predetermined condition must be met.

Abstract: An impending kickback condition in the operation of a power tool or machine tool system is sensed and used to control or eliminate the kickback. The ability to sense an impending kickback condition can be used in all categories of power driven tools. The change in force applied to the power driven tool or other implement is monitored with a microcomputer by measuring the rate of change of current. If the current is increasing, the microcomputer compares the rate of change of current with a threshold value which may be either preset or computed by the microcomputer. If this threshold value is exceeded, an output control signal is generated by the microcomputer which inhibits the coupling of power to the tool or other implement and/or applies a brake to stop the tool or implement. In order for power to once again be coupled to the tool or implement, the start switch must be opened and then reclosed or some other signal provided by the operator or another predetermined condition must be fulfilled.