Abstract: A carrier signal generation section is provided for each of U, V, and W phases, and each of the carrier signal generation sections has an up-down counter for counting clock signals output from a clock generator. An initial value is set for each of the up-down counters. When the up-down counters are simultaneously started by method of a count start signal output from a CPU, the respective up-down counters start counting operations from the respective initial values, perform cumulative subtraction until the count value reaches an upper limit, and perform cumulative addition until the count value reaches a lower limit. As a result, triangular wave carrier signals Cu, Cv and Cw of respective phases having a predetermined phase difference can be readily generated with high accuracy.

Abstract: An interrupt signal is generated at each of rising timings of PWM signals which are produced on the basis of phase-shifted triangular wave carrier signals for phases, and voltage command values for the phases. At timings of the interrupt signals, A/D conversion of motor currents of the phases detected by a shunt is started. Interrupt signals are also produced at timings of valleys of the triangular wave carrier signals. Additionally, peak interrupt signals and valley interrupt signals are respectively produced at timings of peaks and valleys of triangular wave carrier signals for phases. Based on each of the peak interrupt signals, normality/abnormality of a switching element of an upper side of the phase corresponding to the interrupt signal is checked, and, based on each of the valley interrupt signals, normality/abnormality of a switching element of a lower side of the phase corresponding to the interrupt signal is checked.

Abstract: An interrupt signal is generated at each of rising timings of PWM signals which are produced on the basis of phase-shifted triangular wave carrier signals for phases, and voltage command values for the phases. At timings of the interrupt signals, A/D conversion of motor currents of the phases detected by a shunt is started. Interrupt signals are also produced at timings of valleys of the triangular wave carrier signals. Additionally, peak interrupt signals and valley interrupt signals are respectively produced at timings of peaks and valleys of triangular wave carrier signals for phases. Based on each of the peak interrupt signals, normality/abnormality of a switching element of an upper side of the phase corresponding to the interrupt signal is checked, and, based on each of the valley interrupt signals, normality/abnormality of a switching element of a lower side of the phase corresponding to the interrupt signal is checked.

Abstract: A carrier signal generation section is provided for each of U, V, and W phases, and each of the carrier signal generation sections has an up-down counter for counting clock signals output from a clock generator. An initial value is set for each of the up-down counters. When the up-down counters are simultaneously started by method of a count start signal output from a CPU, the respective up-down counters start counting operations from the respective initial values, perform cumulative subtraction until the count value reaches an upper limit, and perform cumulative addition until the count value reaches a lower limit. As a result, triangular wave carrier signals Cu, Cv and Cw of respective phases having a predetermined phase difference can be readily generated with high accuracy.

Abstract: A reach forklift comprises: a forklift body; left and right straddle arms; a pair of load wheels supported in a steerable manner in the vicinity of front ends of the left and right straddle arms, respectively; driving means for steering the load wheels, the load wheels and the driving means being housed in the straddle arms; a drive wheel disposed in a rear portion of the forklift body; and a steering wheel for steering the drive wheel; steering angle detecting means for detecting steering angles of the left and right load wheels and the drive wheel.