How do I calculate an inverse engine torque map from an engine torque map?

I am in the process of designing a torque based control structure for a racing motorcycle. As part of the control structure, a desired torque input has to be converted into a desired throttle angle. I already have the engine torque map, a two-dimensional table correlating throttle angle and RPM with torque (i.e. for a given throttle angle and engine speed, the engine will produce a certain torque). Now I need an inverse engine torque map that allows me to calculate the required throttle opening for the desired torque at the current engine speed).

My question is, what is the most efficient way to derive an _ inverse _ engine torque map from the regular engine torque map. Any suggestions for doing this automatically rather than manually?

Answer 1

[Zikobrelli]

RPM=[500 1000 1500 2000]';

alpha_throttle=[0.1 0.2 0.4 0.8];

torque_map=

[67   89   95   108

   74   92   110  123

   80   97   115  127

   84   106  119  135];
RPM_dmnd=1000;

Torque_dmnd=92;

Z=interp2(RPM,alpha_throttle,torque_map',RPM_dmnd,alpha_throttle);

required_throttle=interp1(Z,alpha_throttle,Torque_dmnd);

[Narayani]

I tried using this code in a 'Matlab m function block' in simulink. It gives me a dimensionality error. However, when executed as a function in MATLAB it works perfectly well. Am I doing something wrong ?

[Zikobrelli]

i'm not very experienced with simulink, but if it works with matlab, it should be ok.Look at your vector dimensions on simulink

[KyoungSeok Han]

I think simulink Matlab m function does not provide the interp1 or interp2 function. How can i find the new look up table about required throttle = f(torque, RPM), namely new table has the following structure, column -> torque (mx1) , raw = RPM(nx1) , table content= throttle (mxn).

Answer 2

[Piyush George Alexander]

Does this work if the torque is not monotonously increasing or decreasing ?

RPM=[500 1000 1500 2000]';

alpha_throttle=[0.1 0.2 0.4 0.8];

torque_map=[67 89 95 108 74 97 97 97 97 97 90 88 85 83 74 65];

surf(RPM,alpha_throttle,torque_map); figure(2) surf(RPM,alpha_throttle,torque_map'); RPM_dmnd=1000; Torque_dmnd=92;

Z=interp2(RPM,alpha_throttle,torque_map,RPM_dmnd,alpha_throttle);

figure(3) plot(Z,alpha_throttle);

required_throttle=interp1(Z,alpha_throttle,Torque_dmnd);