How many degrees-of-freedom does a biped need?

One of the primary motivations for designing a biped robot is to perform tasks in environments that are too dangerous for human beings. To be a satisfactory substitute for a human being the robot must be able to enter a region originally designed for human access and perform tasks that are not already automated and normally require the capabilities of a person. One measure of the success of a biped design is how well it can emulate the agility of a human being. This paper examines the degrees of freedom required for a biped robot to emulate the `most significant´ gaits and standing reflexes of a human counterpart. The first concern is the number of degrees of freedom required to provide a stable platform. Additional degrees-of-freedom will be added to enable the biped to perform locomotion gaits that permit human agility. The actuator torque required for each degree of freedom is also considered