Ambulatory Robotics Lab ARL Monopod I and II specs

Ambulatory Robotics Lab (ARL), Centre for Intelligent Machines, McGill University (Canada) ARL Monopod I and II (1)

Not for sale

Not for sale (research)Not programmableResearchElectric hopperHip springHistoric

Not for saleShipping: Not for sale.

Remote control: Not possible. Historic laboratory machines.

LEARN MORE (McGill ARL Monopod II page, archived) ↗

Overview

Martin Buehler had done a post-doc with Marc Raibert. His McGill lab built the ARL Monopod by adapting the design and control laws of Raibert's hydraulic and pneumatic hoppers to low-power electric motors. Monopod I ran at 1.2 m/s on a treadmill while attached to a low-friction planarizer that kept it in a vertical plane. It averaged 125 W of mechanical power for a specific resistance of 0.7, which its builders called the fastest and most efficient electric legged robot of its day. Its tests showed that 40–50% of that energy went into simply swinging the leg, so Monopod II added rubber springs at the hip. Running as two synchronized passive oscillations, it hopped on its leg spring while the leg and body swung about the hip spring. At 1.25 m/s it used about 48 W at the motor shafts (20.7 J per step), a specific resistance of 0.22. The 1999 paper reports this as the best efficiency of any actively controlled legged robot. These figures leave out motor losses, so electrical input was higher. The same lab went on to build Scout quadrupeds and to work on RHex.

Type: Jumping robot · Jumping & hopping robots
Maker: Ambulatory Robotics Lab (ARL), Centre for Intelligent Machines, McGill University (Canada)
Released: 1992
Price: Not for sale
Status: Not for sale (research)
Best for: Professionals & labs
Programming: No programmability

Price and shipping

University research robots built in Martin Buehler's lab (Monopod I 1992–1994, Monopod II 1993–1997, per the lab's robot list).

Shipping: Not for sale. Not available. Historic university research machines.

Specifications

Category	Jumpers & hoppers · Jumping & hopping robots
Released	1992
Country	Canada
Availability	Not for sale (research)
Programmability	No programmability
Built-in autonomy	None / scripted · Moves only when controlled, or plays preset motions
LLM support	None · No built-in LLM and no SDK to connect one.
Best for	Professionals & labs
Vision sensors	No vision sensors
Actuators	DC / gear motors
Audio	No audio
Compute type	Proprietary / undisclosed
Remote control	Not programmable
Size	Monopod II about 0.7 m tall and 18 kg including 1.9 kg of moving planarizer parts (body 11.5 kg, leg 4.6 kg). Monopod I 15 kg
Locomotion	One prismatic leg, an 80 W brushed Maxon DC motor turns a ball screw in series with a helical compression leg spring. The hip is driven by a second 80 W motor through a timing belt, ball screw and cables over a pulley (30:1, 55 Nm). Monopod II adds natural-rubber surgical-tubing hip springs spliced into the hip cables
Compute	Transputer-based real-time control board issuing motor torque commands at 1 kHz (Monopod I). Monopod II carried an on-board controller, model not published
Camera	None
Sensors	Optical encoders on the leg actuator and body height, a linear potentiometer for leg length in stance (1993 leg design), plus body height, forward travel and pitch measured through the planarizer
Runtime	Monopod I was not power-autonomous. Monopod II carried on-board batteries and controller, but run time was not published (two-minute treadmill runs are reported)
Speed	Monopod I up to 1.2 m/s (4.3 km/h), Monopod II up to 1.25 m/s (4.5 km/h) on a treadmill
SDK	None