Marc-Antoine Legault

Multi-Modal Locomotion Robotic Platform Using Leg-Track-Wheel Articulations

Other than from its sensing and processing capabilities, a mobile robotic platform can be limited in its use by its ability to move in the environment. Legs, tracks and wheels are all efficient means of ground locomotion that are most suitable in different situations. Legs allow to climb over obstacles and change the height of the robot, modifying its viewpoint of the world. Tracks are efficient on uneven terrains or on soft surfaces (snow, mud, etc.), while wheels are optimal on flat surfaces. Our objective is to work on a new concept capable of combining different locomotion mechanisms to increase the locomotion capabilities of the robotic platform. The design we came up with, called AZIMUT, is symmetrical and is made of four independent leg-track-wheel articulations. It can move with its articulations up, down or straight, allowing the robot to deal with three-dimensional environments. AZIMUT is also capable of moving sideways without changing its orientation, making it omnidirectional. By putting sensors on these articulations, the robot can also actively perceive its environment by changing the orientation of its articulations. Designing a robot with such capabilities requires addressing difficult design compromises, with measurable impacts seen only after integrating all of the components together. Modularity at the structural, hardware and embedded software levels, all considered concurrently in an iterative design process, reveals to be key in the design of sophisticated mobile robotic platforms.

Differential elastic actuator for robotic interaction tasks

For complex robotic tasks (e.g., manipulation, locomotion), the lack of knowledge of precise interaction models, the difficulties to precisely measure the task associated physical quantities (e.g., position of contact points, interaction forces) in real-time, the finite sampling time of digital control loops and the non-collocation of sensors and transducers have negative effects on performance and stability of robots when using simple force or simple movement controllers. To cope with these issues, a new compact design for high performance actuators specifically adapted for integration in robotic mechanisms is presented. This design makes use of a mechanical differential as its central element. Results shown that differential coupling between an intrinsically high impedance transducer and an intrinsically low impedance mechanical spring provides the same benefits as serial coupling, but in a more compact and simple design. This new actuator, named Differential Elastic Actuator (DEA), provides interesting design implementations, especially for rotational actuators used for mobile robot locomotion.

AZIMUT, a leg-track-wheel robot

AZIMUT is a mobile robotic platform that combines wheels, legs and tracks to move in three-dimensional environments. The robot is symmetrical and is made of four independent leg-track-wheel articulations. It can move with its articulations up, down or straight, or to move sideways without changing the robots orientation. To validate the concept, the first prototype developed measures 70.5 cm/spl times/70.5 cm with the articulations up. It has a body clearance of 8.4 cm to 40.6 cm depending on the position of the articulations. The design of the robot is highly modular, with distributed embedded systems to control the different components of the robot.

Natural interaction design of a humanoid robot

Designing robots that interact naturally with people requires the integration of technologies and algorithms for communication modalities such as gestures, movement, facial expressions and user interfaces. To understand interdependence among these modalities, evaluating the integrated design in feasibility studies provides insights about key considerations regarding the robot and potential interaction scenarios, allowing the design to be iteratively refined before larger-scale experiments are planned and conducted. This paper presents three feasibility studies with IRL-1, a new humanoid robot integrating compliant actuators for motion and manipulation along with artificial audition, vision, and facial expressions. These studies explore distinctive capabilities of IRL-1, including the ability to be physically guided by perceiving forces through elastic actuators used for active steering of the omnidirectional platform; the integration of vision, motion and audition for an augmented telepresence interface; and the influence of delays in responding to sounds. In addition to demonstrating how these capabilities can be exploited in human-robot interaction, this paper illustrates intrinsic interrelations between design and evaluation of IRL-1, such as the influence of the contact point in physically guiding the platform, the synchronization between sensory and robot representations in the graphical display, and facial gestures for responsiveness when computationally expensive processes are used. It also outlines ideas regarding more advanced experiments that could be conducted with the platform.

Toward autonomous, compliant, omnidirectional humanoid robots for natural interaction in real-life settings

The field of robotics has made steady progress in the pursuit of bringing autonomous machines into real-life settings. Over the last 3 years, we have seen omnidirectional humanoid platforms that now bring compliance, robustness and adaptiveness to handle the unconstrained situations of the real world. However, today’s contributions mostly address only a portion of the physical, cognitive or evaluative dimensions, which are all interdependent. This paper presents an overview of our attempt to integrate as a whole all three dimensions into a robot named Johnny-0. We present Johnny-0’s distinct contributions in simultaneously exploiting compliance at the locomotion level, in grounding reasoning and actions through behaviors, and in considering all possible factors experimenting in the wildness of the real world.

Co-Design of AZIMUT: A Multi-Modal Robotic Platform

AZIMUT is a mobile robotic platform that combines wheels, legs and tracks to move in three-dimensional environments. Its design is the result of an interdisciplinary effort combining expertise in mechanical engineering, electrical engineering, computer engineering and industrial design. After presenting AZIMUT, this paper describes the challenges of designing such a robot, outlining the interdependencies between the disciplines and the difficult compromises that have to be made during the iterative design process of a mobile robotic platform. Modularity at the structural, hardware and embedded software levels, all considered concurrently in an iterative design process, reveals to be key in the design of sophisticated mobile robotic platforms.Copyright

Dual differential rheological actuator for robotic interaction tasks

Robots fail to perform complex manipulation or locomotion tasks when using simple force or motion controllers applied to classic actuators. Stability and safety issues arise for reasons such as high output inertia and the non-collocation of sensing and actuating transducers. This paper presents a new actuation concept, integrating a DC motor and two differentially coupled magnetorheological brakes, promising safe and versatile interaction capabilities. This paper focuses on the underlying mechanism and a case study with a proof-of-concept prototype.

Elastic locomotion of a four steered mobile robot

The most common ground locomotion method to make a mobile robot move is to use two-wheel drive with differential steering and a rear balancing caster. Controlling the two motors independently makes the robot non-holonomic in its motion. Such robots can work well indoor on flat surfaces and in environments adapted for wheelchairs. But the benefit of providing mobility to a robot directly relies on its locomotion capability, for handling different types of terrains (indoors or outdoors) and situations such as moving slowly or rapidly, with or without the presence of moving objects (living or not), climbing over objects and potentially having to deal with hazardous conditions. It is with this objective in mind that we designed AZIMUT. AZIMUT is a legged tracked wheeled robot capable of changing the orientation of its four articulations. Each articulation has three degrees of freedom (DOF): it can rotate 360deg around its point of attachment to the chassis, can change its orientation over 180deg, and rotate to propulse the robot.

Admittance control of a human centered 3 DOF robotic arm using Differential Elastic Actuators

This video shows the functionalities of a 3 serial DOF robotic arm. Each DOF is actuated with a patent pending differential elastic actuator (DEA) [1,2]. Compared to the abundantly studied series elastic actuator [3,4], DEA uses a differential coupling between a high impedance mechanical speed source and a low impedance mechanical spring. Possible implementations of a mechanical differential include the use of a standard gearbox, harmonic drive, cycloidal gearbox, bar mechanism, cable mechanism and all other mechanism that implement a differential function between three mechanical ports. For the implementation reported in this video, we used a harmonic drive for a very compact design. A passive torsion spring (thus the name elastic), with a known impedance characteristic corresponding to the spring stiffness, is used, with an electrical DC brushless motor. A non-turning sensor connected in series with the spring measures the torque output of the actuator.

Johnny-0, a compliant, force-controlled and interactive humanoid autonomous robot

Summary form only given. Johnny-0 [2], shown in Figure 1, is our new humanoid robot which integrates an expressive face on an orientable head, two arms with 4 degrees of freedom (DOF) each and grippers, mounted on an omnidirectional, non-holonomic mobile platform. Our underlying goal with Johnny-0 is to design a platform capable of natural reciprocal interaction (motion, language, touch, affect) with humans, to address integration issues associated with advanced motion, interaction and cognition capabilities on the same platform, and their use in unconstrained real world conditions. To do so, compliance is a necessity to provide natural and safe interactions. One distinctive element of Johnny-0 is that it uses force-controlled actuators (called Differential Elastic Actuators - DEA for active steering of its mobile platform, and for interactive control of its 4-DOF arms. Compliance at the mobile platform level allows a person to physically guide the robot without having to push it from a specific location on the platform [1]. Motion can also be constrained to avoid obstacles and collisions, providing natural physical interaction with the robot. Impedance control of each joint enables infinite combination of arm behaviors, from zero impedance for free movement with gravity compensation, to high stiffness constraining the arms to precise positions or ranges of movement. Stiffness can be configured to create virtual constraints in cartesian space, providing force feedback to the user about movements limitations of the arms. For instance, stiffening the arms in certain poses could indicate to the user that the arms are restrained to move into a specific volume. Beyond these limits, any pushing or pulling force can be perceived by the mobile base, and can be interpreted as an intention to move the robot around. Combining compliance to other sensors (e.g., Kinect motion sensor) and a robot head capable of facial expression allows Johnny-0 to detect incoming people and adjust the impedance of its actuators accordingly (e.g., extend its gripper to greet them), and express its state based on how people physically interact with it (e.g., displaying surprise when the user move the arms beyond specific limits).