Estimating combustion torque of a reciprocating engine utilizing samples of crank acceleration at singularities

In this paper we present a method to estimate combustion torque against a crankshaft angle of a reciprocating engine. We introduce a singular angle of a crankshaft at which an external torque value is sampled directly from crankshaft angular acceleration and show examples for a variety of engines under symmetries. When the bandwidth of external torque signal is less than the Nyquist frequency of periodic sampling, the signal is reconstructed from samples and combustion torque is estimated against a crankshaft angle. Experimental results show good accuracy of the method to monitor actual combustion torque.