Figure 2.

A cruise controller based on PI control under active inference. (a) The response of the car velocity over time with a target state, or prior in our formulation, ${\eta }_x=10$ km/h, ${\eta }_{x^{\prime }}=0$ km/h${}^2$; (b) The acceleration of the car over time with a specified prior ${\eta }_x^{\prime }=0$ km/h${}^2$; (c) The external force v, introduced at $t=150$ s, models a sudden change in the environmental conditions, for instance wind or change in slope. Action obtained via the minimisation of variational free energy with respect to a and counteracts the effects of v. The motor action is never zero since we assume a constant slope, $\lambda =4^{\circ }$ (see Table A1, Appendix A); (d) The model car we implemented, where v could be thought of as a sudden wind or a changing slope.

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(a)	(b)

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(c)	(d)