Posts Tagged ‘Hexapod’

1976 – OSU Hexapod – McGhee (American)

OSU Hexapod p1 x640 1976   OSU Hexapod   McGhee (American)

Earlier 1976 version sans stereo cameras.

OSU Hexapod P5 x640 1976   OSU Hexapod   McGhee (American)

See a few seconds of McGhee's OSU Hexapod in motion in my walking machine compilation video clip.

Stop Press! 20 Oct 2010: Just found fabulous footage of this walker plus others. 50meg download. mp4 runs for 16 mins. see here.

OSU Hexapod RobResearchp1 x640 1976   OSU Hexapod   McGhee (American)

OSU Hexapod RobResearchp2 x640 1976   OSU Hexapod   McGhee (American)

OSU Hexapod RobResearchp3 x640 1976   OSU Hexapod   McGhee (American)

OSU Hexapod RobTech3ap1 x640 1976   OSU Hexapod   McGhee (American)

OSU Hexapod RobTech3ap2 x640 1976   OSU Hexapod   McGhee (American)

OSU RobotTechV3Ap1 x640 1976   OSU Hexapod   McGhee (American)

OSU RobotTechV3Ap2 x640 1976   OSU Hexapod   McGhee (American)

OSU Hexapod Marsh p1 x640 1976   OSU Hexapod   McGhee (American)

McGhee used Electric drill's to power the legs, similar to his earlier 'Phoney Pony'.


From Basic Robotic Concepts by John M. Holland, 1983.

The OSU Hexapod
At Ohio State University, Robert McGhee and his associates have spent a great deal of effort in perfecting a six-legged insectlike drive system called the "Hexapod" . This system is not the first of its kind to be constructed. That distinction probably belongs to the General Electric "Quadruped Transporter," which was a manually operated four-legged walker developed in the late 1960s. In fact, McGhee himself developed a four-legged walker at the University of Southern California in 1967 [RH- see 'Phoney Pony' link above]. The OSU Hexapod is, however, far more sophisticated in its control than any of these earlier projects. At this time its only rival exists in the Soviet Union, but a similar machine is under construction in Japan.
The Hexapod is being used to develop and test control hardware and software. The system is not intended to be independent, and so it is driven by ac line power through the use of triac controls. The Hexapod is kept tethered and is made to walk short distances over obstacles. One of the forelegs is instrumented with a set of strain gauges and is used for the more complex functions. This is in keeping with the very well proven research axiom of simplifying the problem to the basics.
As with most basic research, the most promising thing about the Hexapod is not the device itself, but the new concepts that are being generated and/or verified during its development. One of the most fundamental concepts that has been studied is "active compliance." This concept arises because position control alone is not sufficient for a walking machine since the sensor systems of the robot will not likely know the exact level of the surface of the ground at the point of contact of each foot. Additionally, the surface firmness may vary greatly under different feet. For these reasons, the control algorithm must include the force being exerted on the surface as part of the feedback loop. This is done by adding a second term to the error feedback signal of the control loop.5 For a rotational joint, the simple position error is

     ERROR = K X (θc — θ)
where,
     θc is the commanded angle, θ is the actual position,
     K is the feedback gain.
     This can also be stated as
     ERROR = K X Ea
where,
     Ea is the angular error.
With active compliance, a torque term is added and the equation becomes:
     ERROR = (Ka X Ea) + (Kt X Et)

In this case, the angle and torque are both commanded, and the total error is taken to be a combination of the torque error and the angular error. To understand this consider the case of the vertical plane hip joint of a leg as the leg approaches contact with the ground. If the angular error reaches zero and the foot has not yet touched the surface (the ground is lower than the robot expected), the leg will not stop moving. This is because there is still an error signal to drive it. This signal is supplied by the torque term. Since the foot has not touched the surface, this term has an error contribution to the whole error. Conversely, if the leg touched down prematurely, it would not move all the way to the commanded position as the load torque term would go positive after the torque target was passed. This means that the robot trades off torque for position. This same process is used in the velocity and acceleration control loops of the robot. The ratio of the gains of the two terms (Ka and Kt) gives the compliance ratio. McGhee has found that this factor should best be adjusted for the roughness of the ground. It should be noted that compliance is necessary in the horizontal plane of control as well as in the vertical plane.
Other interesting facts have come to light during the development of the Hexapod. According to McGhee, a walking robot should be more efficient on soft surfaces (such as sand and mud) than a rolling machine. This is because rolling machines (treads included) generate a bow-wave effect. This continuous displacement of material all along the path of motion represents a significant power loss. In actual tests, however, walking machines are far less efficient. This is due to several causes, including the use of worm gears in the joints. McGhee has noted that for a walking robot to be efficient, it must recover the kinetic energy from a limb as it slows the limb's motion relative to the body (especially in the unloaded arc of its movement). Worm gears and most common hydraulic controls are not capable of doing this. Additionally, neither of these is very efficient in the first place! Direct-drive motors with back emf braking and power recovery may provide a partial answer to this problem in the future.
It should be noted that the translation between the desired cartesian forces, motions, and positions and their angular counterparts is nontrivial. The term proprioceptive is used to describe the joint control, and the term exterioceptive is used to describe the vector ground reaction forces. McGhee used Jacobian transforms to develop the relationships between these two systems, but the explanation of these is beyond the scope of this discussion.


1976 – “Masha” Hexapod – Gurfinkel et al (Soviet)

russian walker masha topfotoRIA04 016184 x640 1976   Masha Hexapod   Gurfinkel et al (Soviet)

1977 masha gurfinkel x640 1976   Masha Hexapod   Gurfinkel et al (Soviet)

Masha tm 1990 06p6 x640 1976   Masha Hexapod   Gurfinkel et al (Soviet)

gurfinkel hexapod px x640 1976   Masha Hexapod   Gurfinkel et al (Soviet)

Mascha diag x640 1976   Masha Hexapod   Gurfinkel et al (Soviet)

Masha 1983 x640 1976   Masha Hexapod   Gurfinkel et al (Soviet)

Masha being used in some force-feedback experiments. The experiment here to feed a cylinder into an inclined funnel.

 1976   Masha Hexapod   Gurfinkel et al (Soviet)

See Devjanin-Schneider paper here.


masha p2 x640 1976   Masha Hexapod   Gurfinkel et al (Soviet)

MASHA Gorinevsky p2 x640 1976   Masha Hexapod   Gurfinkel et al (Soviet)

MASHA Gorinevsky x640 1976   Masha Hexapod   Gurfinkel et al (Soviet)

The above three images show experimentation by Gorinevsky.  His paper is available here.

Gorinevsky produced a video of the walking machine. After many media transformations, the quality is poor. See here.   1976   Masha Hexapod   Gurfinkel et al (Soviet)


Masha x640 1976   Masha Hexapod   Gurfinkel et al (Soviet)

Hexapod 1976 RobTech3ap1 x640 1976   Masha Hexapod   Gurfinkel et al (Soviet)

The above  image, I believe, is incorrectly attributed to Bessonov.

Note also the due to incorrect spelling from the old "Walking Machine Catalog", some sites know this walking vehicle as "Mascha".


"Masha", a hexapod walking vehicle an control system designed at the Institute for Mechanics at Moscow State University and at the Institute for Problems of Information Transmission at the USSR Academy of Sciences.


Leningrad hexapods p0 x640 1976   Masha Hexapod   Gurfinkel et al (Soviet)

See here, here, and here for the other Leningrad Mechanical Institute models (links yet to be added).


1969-72 – Six-Legged Walking Machine – Mocci, Petternella, Salinari (Italian)

Peternella 6 legged walker   Copy x640 1969 72   Six Legged Walking Machine   Mocci, Petternella, Salinari (Italian)

Six-legged Walking Machine by Petternella et al. (Instituto di Automatica, Roma, Italia)

Mocci, U., M. Petternella and S. Salinari (1973), "Experiments with six-legged walking machines with fixed gait"

Vukobratovich M. Shagayuschie roboty i antropomorfnye mehanizmy / M. Vukobratovich. – Moscow : Mir, 1976. – 544p.
M.Peternella (Rome, Institute of Automatics) with team of colleagues created the six-legged walking machine with electric drives. There is the interesting constructive decision for legs: hip joint was made in the form of hinge with lateral axis (single degree of freedom), and telescoping of shank is made in area of knee joint. Thus, motion of leg can be the same as one of articulated leg. This model of walking machine is able to do the straight-line movement only. The further improvement is planned.

Kozyrev Y.G. Promyshlennye roboty : Spravochnik / Y.G. Kozyrev. – [2nd edition] – Moscow : Mashinostroenie, 1988. – 392p.
The experimental electromechanical six-legged machine equipped by extremity, which have two degree of freedom – first is rotary (femoral joint), and second (knee joint) has the telescopic sliding structure.
peternella walking machine 1969 72   Six Legged Walking Machine   Mocci, Petternella, Salinari (Italian)

Thanks to Vadym Shvachko in supplying the extra information.


1980 – Hexapod – J.J. Kessis (French)

Hexapod Kessis 1980 RobTech3ap1 x640 1980   Hexapod   J.J. Kessis (French)

Teleoperations and robotics: evolution and development Jean Vertut, Philippe Coiffet – 1986

J.J. Kessis at the University of Paris VII developed an interesting vehicle with six articulated legs, with a pantograph, allowing coordination to be carried out mechanically in the plane of the leg. The high compliance of the chassis is required for turning and non-planar ground, which means that good mobility on ground is not possible.


Real-time control of walking By Marc D. Donner

Kessis has constructed a similar six legged machine in France and it is the subject of continuing research. This machine has six legs with two controlled degrees of freedom each. The problem of permitting the feet to move in the direction of the third degree of freedom in order to permit turning is handled by making the lower legs thin and flexible and letting them bend to comply with the terrain. Control is open loop, with the approach taken to gait control based on the analysis performed by Bessonov.