Motor vehicles – Special driving device – Stepper
Reexamination Certificate
2000-08-02
2003-03-04
Boehler, Anne Marie (Department: 3611)
Motor vehicles
Special driving device
Stepper
C074S005220, C180S007100, C901S001000
Reexamination Certificate
active
06527071
ABSTRACT:
This invention relates to an appliance configured in reverse pendulum in relation to gravity, stabilised by a gyroscope, such as a two-legged robot according to the application given chief consideration.
Mobile robots are of extremely different make-up depending upon their missions and the pathways along which they are likely to travel, but the choice of a good solution raises problems in crowded environments littered with obstacles or with difficult access since the robot must then be provided with equilibrium, agility, flexibility and stability related properties so that it can make its way between obstacles, by-pass them or climb over them. Therefore tracked robots, some with several successive caterpillar axles, have been proposed. In one appliance actually built, the front caterpillar axle was articulated to the remainder of the robot so that it could be raised obliquely and assume the incline of stairs to be mounted: the caterpillar tracks of the front axle gripped several front treads at the same time enabling stair mounting to be initiated. But the drawback of caterpillar vehicles is a relatively large requirement of ground space and difficulty in accurate turning.
Robots mounted on feet or legs have also been put forward. Widely varying designs exist both in respect of the number of feet or legs and in respect of their properties, in particular concerning moving or shape changing possibilities. One extreme construction is a one-legged jumping robot provided with a single foot; this foot is rigid but ends in a jack allowing its periodic extension and it is jointed to a robot body to which it must give support. Sudden extension of the jack throws the robot body in the air and the piloting system adjusts the direction of the foot when it is lifted off the ground in order to prepare the following jump and re-balance the robot or move it in the required direction. Produced prototypes show that this concept is perfectly feasible despite its lack of static stability. However robots are generally preferred which are equipped with a much higher number of feet and six-footed robots have in particular met with real popularity. The six feet are distributed into two groups of three which alternately carry out the same work: one of the groups of feet rests on the ground and maintains the robot body in equilibrium while the other group is lifted and moved forward before being lowered to provide new support to the robot ahead of the previous support, which enables the robot body to be moved forward when the first group of feet is lifted. This is a very stable construction since the feet of each of the groups are arranged in a triangular base within which the centre of gravity of the robot is always contained. But this stable equilibrium is obtained at the price of the robot's complexity, large space requirement and relatively considerable weight.
There is a temptation, however, to recall that artificial environments such as factories, in which numerous robots need to move around, were firstly designed for man, and to draw the conclusion that a robot imitating the form and walk of man as near as possible should give the best results by offering a satisfactory compromise between complex robots that are highly stable but voluminous and robots with a reduced number of feet whose equilibrium raises problems. Experience has shown that two-legged robots, made up of legs articulated independently from the robot body and fitted with a knee joint for alternate flexing and extension to imitate man's walk, require less space and can be of use in difficult, complicated situations by overcoming varied obstacles. Strict co-ordination however of the different motors controlling the articulations is required to maintain equilibrium, and imitation -of man's walk is less easy than may be thought.
The purpose of the invention is therefore to bring radical improvement to the stability of appliances having relatively unstable equilibrium, for example those configured in reverse pendulum such as one-legged, two-legged or even three-legged robots, since at certain times during their movement they are only supported by two legs, by equipping them with a gyroscopic rotor wheel located in an upper body supported by the leg or legs. The gyroscopic rotor wheel forms a “inertial fulcrum point” which, for an appliance whose static equilibrium is not assured, fulfils the same role as a balancing pole for a tightrope walker; the invention also comprises the automatism parts which make use of this fulcrum point (sensors or detectors, command system, actuators positioned between the balancing pole and the tightrope walker to use the former image) in order to balance the appliance in any position for a certain period of time. In other words, the invention also enables stability to be imparted to the reverse pendulum appliance at any time, even if the supporting leg is strongly inclined, provided however that certain operating conditions are met.
This rotor wheel, intended to assure equilibrium, is to be distinguished from the gyrometer of the robot in the article published by Matsumoto et al “A four-wheeled robot to pass over steps by changing running control modes” (IEEE International Conference, May 21, 1995, p. 1700 to 1706) which only serves to measure its tilt when in dynamic equilibrium and in no way contributes towards this equilibrium.
The operating conditions of the rotor wheel are related to the orientation of its spin axis, either relative to gravity or relative to the mechanical suspension between the rotor wheel casing and the upper body (for a one-legged appliance) or the intermediate body (for an appliance with at least two legs). These vary continually taking into account that the spin axis of the rotor wheel drifts under the effect of precession. In particular, this drift limits the time interval in which it is possible to immobilise the appliance in a position in which its supporting leg is strongly inclined. It is possible to correct this effect by voluntary shifting of the whole appliance into a symmetrical configuration (or a series of configurations whose resultant is symmetrical) relative to the equilibrium configuration of the reverse pendulum, either by a strong tilt maintained for a short period of time, or by a less inclined tilt maintained for a longer time interval. It can therefore be seen that the invention is particularly well adapted to the stabilisation of a walking two-legged robot which naturally alternates tilting.
The gyroscopic rotor wheel is placed in a casing, itself connected to the upper body of the appliance by a mechanical suspension which allows rotating movements about two nonparallel axes. This suspension with two nonparallel axes is equipped with actuators able at any time to exert, between the rotor wheel casing and the upper body of the appliance, a stabilising couple which opposes the off-balance effect produced by gravity on the appliance.
The command system adapted to the invention is able to measure the tilt effect produced by gravity on the appliance, to give a command for opposing action to the activators appropriate to achieve perfect balance of the appliance, and to maintain this appliance within its operating conditions. It is also able to co-operate with another command system, such as a system intended to command forward movement of the robot, the latter system therefore being released of the function consisting of seeking and maintaining equilibrium.
This task separation between the two command systems, one managing the robot's equilibrium and the other its forward movement, is an important advantage of the invention which makes co-operation between the systems easy by doing away with the need for their coordination or strict synchronisation. It sets itself well apart from the invention in the article “The walking gyro” (Robotics Age, vol. 7, No. 1, January 1985, pages 7 to 10, Peterborough, NH, USA) in which a gyroscopic rotor wheel undergoes tilting whose effect is to incline a rod in the form of a balancing pole at whose ends are fix
Boehler Anne Marie
Commissariat A L'Energie Atomique
Thelen Reid & Priest LLP
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