  We present several new easy ways of generating smooth one-dimensional maps
displaying robust chaos, i.e., chaos for whole intervals of the parameter.
Unlike what happens with previous methods, the Lyapunov exponent of the maps
constructed here varies widely with the parameter. We show that the condition
of negative Schwarzian derivative, which was used in previous works, is not a
necessary condition for robust chaos. Finally we show that the maps constructed
in previous works have always the Lyapunov exponent $\ln 2$ because they are
conjugated to each other and to the tent map by means of smooth homeomorphisms.
In the methods presented here, the maps have variable Lyapunov coefficients
because they are conjugated through non-smooth homeomorphisms similar to
Minkowski's question mark function.
