Imperial College London

Dr Nicolas Rojas

Faculty of EngineeringDyson School of Design Engineering

Lecturer
 
 
 
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Contact

 

n.rojas

 
 
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Location

 

10-12 Prince's GardensSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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39 results found

Kanner OY, Rojas N, Odhner LU, Dollar AMet al., 2017, Adaptive Legged Robots Through Exactly Constrained and Non-Redundant Design, IEEE Access, Vol: 5, Pages: 11131-11141

JOURNAL ARTICLE

Ward-Cherrier B, Rojas N, Lepora NF, 2017, Model-Free Precise in-Hand Manipulation with a 3D-Printed Tactile Gripper, IEEE Robotics and Automation Letters, Vol: 2, Pages: 2056-2063

JOURNAL ARTICLE

Ma RR, Rojas N, Dollar AM, 2016, Spherical Hands: Toward Underactuated, In-Hand Manipulation Invariant to Object Size and Grasp Location, Journal of Mechanisms and Robotics, Vol: 8, Pages: 061021-061021, ISSN: 1942-4302

JOURNAL ARTICLE

Ma RR, Rojas N, Dollar AM, 2016, Towards Predictable Precision Manipulation of Unknown Objects with Underactuated Fingers, Advances in Reconfigurable Mechanisms and Robots II, Editors: Ding, Kong, Dai, Cham, Publisher: Springer International Publishing, Pages: 927-937, ISBN: 978-3-319-23327-7

BOOK CHAPTER

Rojas N, Dollar AM, 2016, Classification and Kinematic Equivalents of Contact Types for Fingertip-Based Robot Hand Manipulation, Journal of Mechanisms and Robotics, Vol: 8, Pages: 041014-041014, ISSN: 1942-4302

JOURNAL ARTICLE

Rojas N, Dollar AM, 2016, Gross Motion Analysis of Fingertip-Based Within-Hand Manipulation, IEEE Transactions on Robotics, Vol: 32, Pages: 1009-1016, ISSN: 1552-3098

JOURNAL ARTICLE

Rojas N, Ma RR, Dollar AM, 2016, The GR2 Gripper: An Underactuated Hand for Open-Loop In-Hand Planar Manipulation, IEEE Transactions on Robotics, Vol: 32, Pages: 763-770, ISSN: 1552-3098

JOURNAL ARTICLE

Sosa R, Rojas N, Gero JS, Xu Qet al., 2016, Visual divergence in humans and computers, Design Studies, Vol: 42, Pages: 56-85, ISSN: 0142-694X

JOURNAL ARTICLE

Kanner OY, Rojas N, Dollar AM, 2015, Design of a Passively-Adaptive Three Degree-of-Freedom Multi-Legged Robot With Underactuated Legs, ASME 2015 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference (IDETC/CIE), Pages: V05AT08A062-V05AT08A062

This paper discusses the design of a three degree-of-freedom (3-DOF) non-redundant walking robot with decoupled stance and propulsion locomotion phases that is exactly constrained in stance and utilizes adaptive underactuation to robustly traverse terrain of varying ground height. Legged robots with a large number of actuated degrees of freedom can actively adapt to rough terrain but often end up being kinematically overconstrained in stance, requiring complex redundant control schemes for effective locomotion. Those with fewer actuators generally use passive compliance to enhance their dynamic behavior at the cost of postural control and reliable ground clearance, and often inextricably link control of the propulsion of the robot with control of its posture. In this paper we show that the use of adaptive underactuation techniques with constraint-based design synthesis tools allows for lighter and simpler lower mobility legged robots that can adapt to the terrain below them during the swing phase yet remain stable during stance and that the decoupling of stance and propulsion can greatly simplify their control. Simulation results of the swing phase behavior of the proposed 3-DOF decoupled adaptive legged robot as well as proof-of-concept experiments with a prototype of its corresponding stance platform are presented and validate the suggested design framework.

CONFERENCE PAPER

N Rojas, J Borràs, F Thomas, 2015, On quartically-solvable robots, 2015 IEEE International Conference on Robotics and Automation (ICRA), Publisher: Institute of Electrical and Electronics Engineers (IEEE), Pages: 1410-1415, ISSN: 1050-4729

This paper presents a first attempt at a unified kinematics analysis of all serial and parallel solvable robots, that is, robots whose position analysis can be carried out without relying on numerical methods. The efforts herein are focused on finding a unified formulation for all quartically-solvable robots, as all other solvable robots can be seen as particular cases of them. The first part is centered on the quest for the most general quartically-solvable parallel and serial robots. As a result, representatives of both classes are selected. Then, using Distance Geometry, it is shown how solving the forward kinematics of the parallel representative is equivalent to solve the inverse kinematics of the serial representative, thus providing a unified formulation. Finally, it is shown that the position and singularity analysis of these robots reduces to the analysis of the relative position of two coplanar ellipses.

CONFERENCE PAPER

Nansai S, Mohan RE, Tan N, Rojas N, Iwase Met al., 2015, Dynamic Modeling and Nonlinear Position Control of a Quadruped Robot with Theo Jansen Linkage Mechanisms and a Single Actuator, Journal of Robotics, Vol: 2015, Pages: 1-15, ISSN: 1687-9600

JOURNAL ARTICLE

Nansai S, Rojas N, Elara MR, Sosa R, Iwase Met al., 2015, A novel approach to gait synchronization and transition for reconfigurable walking platforms, Digital Communications and Networks, Vol: 1, Pages: 141-151, ISSN: 2352-8648

JOURNAL ARTICLE

Nansai S, Rojas N, Elara MR, Sosa R, Iwase Met al., 2015, On a Jansen leg with multiple gait patterns for reconfigurable walking platforms, Advances in Mechanical Engineering, Vol: 7, Pages: 168781401557382-168781401557382, ISSN: 1687-8140

JOURNAL ARTICLE

Rojas N, Dollar AM, 2015, The Coupler Surface of the RSRS Mechanism, Journal of Mechanisms and Robotics, Vol: 8, Pages: 014505-014505, ISSN: 1942-4302

JOURNAL ARTICLE

Rojas N, Dollar AM, Thomas F, 2015, A unified position analysis of the Dixon and the generalized Peaucellier linkages, Mechanism and Machine Theory, Vol: 94, Pages: 28-40, ISSN: 0094-114X

JOURNAL ARTICLE

Tan N, Rojas N, Elara Mohan R, Kee V, Sosa Ret al., 2015, Nested Reconfigurable Robots: Theory, Design, and Realization, International Journal of Advanced Robotic Systems, Vol: 12, Pages: 110-110, ISSN: 1729-8814

JOURNAL ARTICLE

M R Elara, N Rojas, A Chua, 2014, Design principles for robot inclusive spaces: a case study with Roomba, 2014 IEEE International Conference on Robotics and Automation (ICRA), Publisher: Institute of Electrical and Electronics Engineers (IEEE), Pages: 5592-5599, ISSN: 1050-4729

Research focus on service robots that deals with applications related to healthcare, logistics, residential, search and rescue are gaining significant momentum in the recent years. Their social and economic relevance is more than evident. Yet, while much has been researched about “designing robots” focusing on sensing, actuation, mobility and control of service robots, little work has been done on “design for robots” that looks at designing preferred artefacts or environments for such robots. In this work, we propose a new philosophy of robot inclusive spaces, a cross disciplinary approach that brings together roboticians, architects and designers to solve numerous unsettled research problems in robotics community through design of inclusive interior spaces for robots where the latter live and operate. With a residential floor cleaning robot as a case study, we inductively derived a set of four design principles namely observability, accessibility, activity and safety that guides the realization of an inclusive space for these service robots. Also, the suggested principles are further defined, analysed and validated for their merits in this paper.

CONFERENCE PAPER

N Rojas, A M Dollar, 2014, Characterization of the precision manipulation capabilities of robot hands via the continuous group of displacements, 2014 IEEE/RSJ International Conference on Intelligent Robots and Systems, Publisher: IEEE, Pages: 1601-1608, ISSN: 2153-0858

In robot hands, precision manipulation, defined as repositioning of a grasped object within the hand workspace without breaking or changing contact, is a fundamental operation for the accomplishment of highly dexterous manipulation tasks. This paper presents a method to characterize the precision manipulation capabilities of a given robot hand regardless of the particularities of the grasped object. The technique allows determining the composition of the displacement manifold (finite motion) of the grasped object relative to the palm of the robot hand and defining the displacements that can actually be controlled by the hand actuators without depending on external factors to the hand. The approach is based on a reduction of the graph of kinematic constraints related to the hand-object system through proper manipulations of the continuous subgroups of displacements generated by the hand joints and contacts. The proposed method is demonstrated through three detailed and constructive examples of common architectures of simplified multi-fingered hands.

CONFERENCE PAPER

V Kee, N Rojas, M R Elara, R Sosaet al., 2014, Hinged-Tetro: A self-reconfigurable module for nested reconfiguration, 2014 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, Pages: 1539-1546, ISSN: 2159-6247

CONFERENCE PAPER

M R Elara, N Rojas, R Sosa, J Kaisneret al., 2013, Robot Inclusive Space challenge: A design initiative, 2013 6th IEEE Conference on Robotics, Automation and Mechatronics (RAM), Pages: 73-78, ISSN: 2158-2181

CONFERENCE PAPER

Mohan RE, Rojas N, Seah S, Sosa Ret al., 2013, Design principles for robot inclusive spaces, 19th International Conference on Engineering Design (ICED13)

CONFERENCE PAPER

N Rojas, F Thomas, 2013, The closure condition of the double banana and its application to robot position analysis, 2013 IEEE International Conference on Robotics and Automation, Publisher: Institute of Electrical and Electronics Engineers (IEEE), Pages: 4641-4646, ISSN: 1050-4729

A double banana is defined as the bar-and-joint assembly of two bipyramids joined by their apexes. Clearly, the bar lengths of this kind of assembly are not independent as we cannot assign arbitrary values to them. This dependency can be algebraically expressed as a closure condition fully expressed in terms of bar lengths. This paper is devoted to its derivation and to show how its use simplifies the position analysis of many well-known serial and parallel robots thus providing a unifying treatment to apparently disparate problems. This approach permits deriving the univariate polynomials, needed for the closed-form solution of these position analysis problems, without relying on trigonometric substitutions or difficult variable eliminations.

CONFERENCE PAPER

Rojas N, Mohan R, Sosa R, 2013, Reconfiguration in linkages by variable allocation of joint positions: a modular design approach, 3rd IFToMM International Symposium on Robotics and Mechatronics, Pages: 587-596

CONFERENCE PAPER

Rojas N, Thomas F, 2013, The Univariate Closure Conditions of All Fully Parallel Planar Robots Derived From a Single Polynomial, IEEE Transactions on Robotics, Vol: 29, Pages: 758-765, ISSN: 1552-3098

JOURNAL ARTICLE

Rojas N, Thomas F, 2013, Application of Distance Geometry to Tracing Coupler Curves of Pin-Jointed Linkages 1, Journal of Mechanisms and Robotics, Vol: 5, Pages: 021001-021001, ISSN: 1942-4302

JOURNAL ARTICLE

S Nansai, N Rojas, M R Elara, R Sosaet al., 2013, Exploration of adaptive gait patterns with a reconfigurable linkage mechanism, 2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, Pages: 4661-4668, ISSN: 2153-0858

CONFERENCE PAPER

N Rojas, J Borràs, F Thomas, 2012, The octahedral manipulator revisited, 2012 IEEE International Conference on Robotics and Automation, Pages: 2293-2298, ISSN: 1050-4729

CONFERENCE PAPER

Rojas N, Thomas F, 2012, Formulating Assur kinematic chains as projective extensions of Baranov trusses, Mechanism and Machine Theory, Vol: 56, Pages: 16-27, ISSN: 0094-114X

JOURNAL ARTICLE

Rojas N, Thomas F, 2012, On closed-form solutions to the position analysis of Baranov trusses, Mechanism and Machine Theory, Vol: 50, Pages: 179-196, ISSN: 0094-114X

JOURNAL ARTICLE

Rojas N, Thomas F, 2011, Closed-Form Solution to the Position Analysis of Watt–Baranov Trusses Using the Bilateration Method, Journal of Mechanisms and Robotics, Vol: 3, Pages: 031001-031001, ISSN: 1942-4302

JOURNAL ARTICLE

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