Motor speed control apparatus for an electrically powered vehicle

Claim 2

In a battery-powered vehicle having a traction motor for propelling said vehicle and an auxiliary motor for driving cutting tools associated therewith, apparatus comprising: battery means including a battery for applying a DC potential to said traction motor and said auxiliary motor; stabilizing means coupled intermediate said battery means and said traction motor for receiving said DC potential from said battery means and applying a stabilized DC potential to said traction motor, said stabilizing means including: a. switching mode regulator means coupled to said battery means for stabilizing said DC potential and applying said stabilized DC potential to said traction motor, said switching mode regulator means including means for generating a pulse train having a variable duty cycle, said stabilized DC potential developed by said switching mode regulator means being proportional to said duty cycle; b. amplifier means indluding an operational amplifier with input and output terminals and having means for establishing a preselected potential level at which said stabilized DC potential is to be maintained, said amplifier means further including means for coupling said stabilized DC potential from said switching mode regulator means To said operational amplifier input terminal, said operational amplifier developing an error signal at said output terminal representative of any deviation of said stabilized DC potential from said preselected potential level; and c. gating means coupled intermediate said operational amplifier output terminal and said switching mode regulator means and responsive to said error signal for controlling said pulse train duty cycle to maintain said stabilized DC potential at said preselected potential level; current limiting means coupled to said traction motor and said auxiliary motor and including means for establishing maximum traction motor and auxiliary motor current threshold levels, said current limiting means monitoring the current through both of said motors and generating a control signal whenever said current through either of said motors exceeds the corresponding one of said maximum current threshold levels, said control signal being coupled to said operational amplifier input terminal to modify said error signal developed by said operational amplifier and thereby effect a reduction in the level of said stabilized DC potential applied to said traction motor by said switching mode regulator means; and high-speed comparator means coupled to said traction motor and including means for establishing a maximum instantaneous current threshold level, said high-speed comparator means monitoring the instantaneous current through said traction motor and disabling said switching mode regulator means whenever said instantaneous current exceeds said maximum instantaneous current threshold level thereby interrupting the application of said stabilized DC potential to said traction motor.

Claim 3

In a battery-powered vehicle having a traction motor for propelling said vehicle and an auxiliary motor for driving cutting tools associated therewith, apparatus comprising: battery means including a battery for applying a DC potential to said traction motor and said auxiliary motor; stabilizing means coupled intermediate said battery means and said traction motor for receiving said DC potential from said battery means and applying a stabilized DC potential to said traction motor, said stabilizing means including: a. switching mode regulator means coupled to said battery means for stabilizing said DC potential and applying said stabilized DC potential to said traction motor, said switching mode regulator means including means for generating a pulse train having a variable duty cycle, said stabilized DC potential developed by said switching mode regulator means proportional to said duty cycle; b. amplifier means including an operational amplifier with input and output terminals and having means for establishing a preselected potential level at which said stabilized DC potential is to be maintained, said amplifier means further including means for coupling said stabilized DC potential from said switching mode regulator means to said operational amplifier input terminal, said operational amplifier developing an error signal at said output terminal representative of any deviation of said stabilized DC potential from said preselected potential level; and c. gating means including a logic gate with input and output terminals and having a switching threshold, said gating means further including means for generating a sawtooth voltage waveform and AC coupling said sawtooth voltage waveform to said logic gate input terminal and means for DC coupling said error signal from said operational amplifier output terminal to said logic gate input terminal, said error signal setting the DC level of said sawtooth voltage waveform to determine what portion of said sawtooth voltage waveform exceeds said logic gate switching threshold, said logic gate generating output pulses during intervals when said sawtooth voltage waveform exceeds said logic gate switching threshold, said logic gate output pulses having pulse widths corresponding to the levEl of said error signal, said logic gate output pulses being coupled to said switching mode regulator means to maintain said switching mode regulator means pulse train duty cycle constant; current limiting means coupled to said traction motor and said auxiliary motor and including means for establishing maximum traction motor and auxiliary motor current threshold levels, said current limiting means monitoring the current through both of said motors and generating a control signal whenever said current through either of said motors exceeds the corresponding one of said maximum current threshold levels, said control signal being coupled to said operational amplifier input terminal to modify said error signal developed by said operational amplifier and thereby effect a reduction in the level of said stabilized DC potential applied to said traction motor by said switching mode regulator means; and high-speed comparator means coupled to said traction motor and including means for establishing a maximum instantaneous current threshold level, said high-speed comparator means monitoring the instantaneous current through said traction motor and disabling said switching mode regulator means whenever said instantaneous current exceeds said maximum instantaneous current threshold level thereby interrupting the application of said stabilized DC potential to said traction motor.

Claim 4

In a battery-powered vehicle having a traction motor for propelling said vehicle and an auxiliary motor for driving cutting tools associated therewith, apparatus comprising: battery means including a battery for applying a DC potential to said traction motor and said auxiliary motor; stabilizing means coupled intermediate said battery means and said traction motor for receiving said DC potential from said battery means and applying a stabilized DC potential to said traction motor, said stabilizing means including: a. switching mode regulator means coupled to said battery means for stabilizing said DC potential and applying said stabilized DC potential to said traction motor, said switching mode regulator means including means for generating a pulse train having a variable duty cycle, said stabilized DC potential developed by said switching mode regulator means proportional to said duty cycle; b. amplifier means including an operational amplifier with input and output terminals and having means for establishing a preselected potential level at which said stabilized DC potential is to be maintained, said amplifier means further including means for coupling said stabilized DC potential from said switching mode regulator means to said operational amplifier input terminal, said operational amplifier developing an error signal at said output terminal representative of any deviation of said stabilized DC potential from said preselected potential level; and c. gating means including a logic gate with input and output terminals and having a switching threshold, said gating means further including means for generating a sawtooth voltage waveform and AC coupling said sawtooth voltage waveform to said logic gate input terminal and means for DC coupling said error signal from said operational amplifier output terminal to said logic gate input terminal, said error signal setting the DC level of said sawtooth voltage waveform to determine what portion of said sawtooth voltage waveform exceeds said logic gate switching threshold, said logic gate generating output pulses during intervals when said sawtooth voltage waveform exceeds said logic gate switching threshold, said logic gate output pulses having pulse widths corresponding to the levEl of said error signal, said logic gate output pulses being coupled to said switching mode regulator means to maintain said switching mode regulator means pulse train duty cycle constant; current limiting means coupled to said traction motor and said auxiliary motor and including means for establishing maximum traction motor and auxiliary motor current threshold levels, said current limiting means monitoring the current through both of said motors and generating a control signal whenever said current through either of said motors exceeds the corresponding one of said maximum current threshold levels, said control signal being coupled to said operational amplifier input terminal to modify said error signal developed by said operational amplifier and thereby effect a reduction in the level of said stabilized DC potential applied to said traction motor by said switching mode regulator means; and high-speed comparator means coupled to said traction motor and including means for establishing a maximum instantaneous current threshold level, said high-speed comparator means monitoring the instantaneous current through said traction motor and disabling said switching mode regulator means whenever said instantaneous current exceeds said maximum instantaneous current threshold level thereby interrupting the application of said stabilized DC potential to said traction motor.

Claim 5

Apparatus in accordance with claim 2 wherein said current limiter means includes first amplifier means coupled intermediate said traction motor and said stabilizing means operational amplifier input terminal and further includes second amplifier means coupled intermediate said auxiliary motor and said stabilizing means operational amplifier input terminal, said first amplifier means monitoring said traction motor current and generating said control signal whenever said traction motor current exceeds said maximum traction motor current threshold level and said second amplifier means monitoring said auxiliary motor current and generating said control signal whenever said auxiliary motor current exceeds said maximum auxiliary motor current threshold level.

Claim 6

Apparatus in accordance with claim 3 including means comprising a first resistive element coupled in series with said traction motor for developing a voltage analog thereacross representative of said current drawn by said traction motor and a second resistive element coupled in series with said auxiliary motor for developing a voltage analog thereacross representative of said current drawn by said auxiliary motor and wherein said first and second amplifier means each comprise an operational amplifier having input and output terminals, said first operational amplifier input terminals and said second operational amplifier terminals being coupled across said first resistive element and said second resistive element respectively and said first and second operational amplifier output terminals being coupled to said input terminal of said operational amplifier in said stabilizing means.

Claim 7

Apparatus in accordance with claim 4 including accelerator means for selectively varying said preselected potential level at which said stabilized DC potential is maintained by said amplifier means in said stabilizing means, said accelerator means being coupled to said stabilizing means operational amplifier input terminal by means comprising a pair of series-connected resistors having a common junction, said first and second current limiting operational amplifier output terminals being coupled to said junction, said first and second operational amplifiers having a low output impedance relative to the impedance of said series-connected resistors so that either of said current limiting amplifier control signal overrides said accelerator means to modify said preselected potential level.

Claim 8

Apparatus in accordance with claim 2 wherein said high-speed comparator means comprises amplifier means including an operational amplifier with input terminals coupled to saiD traction motor and switch means coupling said amplifier means to said gating means, said amplifier means generating an output signal whenever said instantaneous current through said traction motor exceeds said maximum instantaneous current threshold level, said switch means disabling said gating means responsive to said output signal to block the application of said logic gate output pulses to said switching mode regulator means thereby interrupting spplication of said stabilized DC potential to said traction motor by said switching mode regulator means.

Claim 9

Apparatus in accordance with claim 6 wherein said switch means comprises a flip-flop having an input terminal coupled to said amplifier means and an output terminal and wherein said gating means includes a second logic gate having a first and second input terminals coupled to said output terminal of said first logic gate and a said flip-flop output terminal respectively and an output terminal coupled to said switching mode regulator means, said flip-flop disabling said second logic gate responsive to said high-speed comparator amplifier means generating said output signal when said traction motor current exceeds said maximum instantaneous current threshold level.

Claim 10

Apparatus in accordance with claim 7 including clock means generating clock pulses, said clock pulses being coupled to said flip-flop to periodically reset said flip-flop thereby enabling said second logic gate so that said first logic gate output pulses are coupled to said switching mode regulator means, said switching mode regulator means being enable to apply said stabilized DC potential to said traction motor.