Torque measurement method and apparatus

A ground engaging vehicle, comprising:

• a power supplying device;
• a load;
• and
• a torque measurement device connected between said power supplying device and said load, the torque measurement device including:
• a rotatable shaft having a longitudinal axis, a first end and a second end, said first end connected to the power supplying device, said second end connected to the load;
• a first detectable feature associated with a first longitudinal position of said shaft;
• a second detectable feature associated with a second longitudinal position of said shaft;
• a plurality of sensors including a first sensor and a second sensor, said first sensor proximate to said first detectable feature, said second sensor proximate to said second detectable feature, said first sensor producing a first signal and said second sensor producing a second signal as said rotatable shaft rotates about said longitudinal axis;
• and
• an electrical controller sampling said first signal and said second signal at a sampling rate, said first signal having a first frequency, said sampling rate being less than twice said first frequency, said electrical controller computing a torque measurement representative of the torque on said rotatable shaft from said first signal and said second signal.

A torque measurement method, comprising the steps of:

• acquiring a plurality of pulse trains including a first pulse train and a second pulse train;
• computing a Fourier coefficient for both said first pulse train and said second pulse train each for a known frequency;
• and
• determining the torque measurement using said Fourier coefficient associated with said first pulse train and said Fourier coefficient associated with said second pulse train.