Helicopter wheels do not have power. Taxiing is accomplished by using the thrust from rotors- for example, in case of CH-47, with rotors at normal rpm, the helicopter will have some forward speed (5-6 kt) with controls at neutral and thrust control rod at ground detent. Steering is usually using pedals (some helicopters have hydraulic steering) and there are, of course brakes (which are used to control taxi using differential braking in some cases).
As you mentioned CH-47, it is interesting to know that there are different ways to taxi the helicopter under different conditions. For example, according to the operator's manual,
Taxiing with two aft gear on the Ground
... Displace the cyclic stick aft approximately 2 inches and increase the thrust till the forward landing gear is off the ground the helicopter begins to move. Maintain directional control with the directional pedals. Control taxi by adjusting the thrust control rod.
Taxiing with power steering
... After the helicopter has started to roll, the thrust control rod should be lowered to the ground detent. This amount of thrust and braking will maintain a moderate taxi speed. ... Turns are initiated by slowly rotating the control knob a small amount and then gradually increasing the knob rotation until the desired turn is reached.
There are separate procedures for hover taxiing and water taxiing, though they don't make use of wheels.