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Intuitive Control of a Planar Bipedal Walking Robot
 Proceedings of the IEEE International Conference on Robotics and Automation
, 1998
"... Bipedal robots are difficult to analyze mathematically. However, successful control strategies can be discovered using simple physical intuition and can be described in simple terms. Five things have to happen for a planar bipedal robot to walk. Height has to be stabilized. Pitch has to be stabilize ..."
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Cited by 53 (5 self)
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Bipedal robots are difficult to analyze mathematically. However, successful control strategies can be discovered using simple physical intuition and can be described in simple terms. Five things have to happen for a planar bipedal robot to walk. Height has to be stabilized. Pitch has to be stabilized. Speed has to be stabilized. The swing leg has to move so that the feet are in locations which allow for the stability of height, pitch, and speed. Finally, transitions from support leg to support leg must occur at appropriate times. If these five objectives are achieved, the robot will walk. A number of different intuitive control strategies can be used to achieve each of these five objectives. Further, each strategy can be implemented in a variety of ways. We present several strategies for each objective which we have implemented on a bipedal walking robot. Using these simple intuitive strategies, we have compelled a seven link planar bipedal robot, called Spring Flamingo, to walk. The r...
Exploiting Inherent Robustness and Natural Dynamics in the Control of Bipedal Walking Robots
, 2000
"... Walking is an easy task for most humans and animals. Two characteristics which make it easy are the inherent robustness (tolerance to variation) of the walking problem and the natural dynamics of the walking mechanism. In this thesis we show how understanding and exploiting these two characteristics ..."
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Cited by 44 (2 self)
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Walking is an easy task for most humans and animals. Two characteristics which make it easy are the inherent robustness (tolerance to variation) of the walking problem and the natural dynamics of the walking mechanism. In this thesis we show how understanding and exploiting these two characteristics can aid in the control of bipedal robots. Inherent robustness allows for the use of simple, low impedance controllers. Natural dynamics reduces the requirements of the controller. We present a series of simple physical models of bipedal walking. The insight gained from these models is used in the development of three planar (motion only in the sagittal plane) control algorithms. The first uses simple strategies to control the robot to walk. The second exploits the natural dynamics of a kneecap, compliant ankle, and passive swingleg. The third achieves fast swing of the swingleg in order to enable the robot to walk quickly (1.25 m s ). These algorithms are implemented on Spring Flamingo...
Programmable Central Pattern Generators: an application to biped locomotion control
 In Proceedings of the 2006 ieee international conference on robotics and automation
, 2006
"... Abstract — We present a system of coupled nonlinear oscillators to be used as programmable central pattern generators, and apply it to control the locomotion of a humanoid robot. Central pattern generators are biological neural networks that can produce coordinated multidimensional rhythmic signals, ..."
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Cited by 34 (14 self)
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Abstract — We present a system of coupled nonlinear oscillators to be used as programmable central pattern generators, and apply it to control the locomotion of a humanoid robot. Central pattern generators are biological neural networks that can produce coordinated multidimensional rhythmic signals, under the control of simple input signals. They are found both in vertebrate and invertebrate animals for the control of locomotion. In this article, we present a novel system composed of coupled adaptive nonlinear oscillators that can learn arbitrary rhythmic signals in a supervised learning framework. Using adaptive rules implemented as differential equations, parameters such as intrinsic frequencies, amplitudes, and coupling weights are automatically adjusted to replicate a teaching signal. Once the teaching signal is removed, the trajectories remain embedded as the limit cycle of the dynamical system. An interesting aspect of this approach is that the learning is completely embedded into the dynamical system, and does not require external optimization algorithms. We use our system to encapsulate rhythmic trajectories for biped locomotion with a simulated humanoid robot, and demonstrate how it can be used to do online trajectory generation. The system can modulate the speed of locomotion, and even allow the reversal of direction (i.e. walking backwards). The integration of sensory feedback allows the online modulation of trajectories such as to increase the basin of stability of the gaits, and therefore the range of speeds that can be produced. I.
Exploiting natural dynamics in the control of a 3d bipedal walking simulation
 In In Proc. of Int. Conf. on Climbing and Walking Robots (CLAWAR99
, 1999
"... Natural dynamics can be exploited in the control of bipedal walking robots: the swing leg can swing freely once started; a kneecap can be used to prevent the leg from inverting; and a compliant ankle can be used to naturally transfer the center of pressure along the foot and help in toe off. Each of ..."
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Cited by 33 (2 self)
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Natural dynamics can be exploited in the control of bipedal walking robots: the swing leg can swing freely once started; a kneecap can be used to prevent the leg from inverting; and a compliant ankle can be used to naturally transfer the center of pressure along the foot and help in toe off. Each of these mechanisms helps make control easier to achieve and results in motion that is smooth and natural looking. We describe a simple control algorithm using these natural mechanisms which requires very little computation. The necessary sensing consists of joint angles and velocities, body pitch and angular velocity, and ground reaction forces. This algorithm is an extension to the algorithm we presented in [16] for a planar walker. To control lateral stability, we use lateral foot placement and ankle torque. Using this simple algorithm, we have controlled a seven link, twelve degree of freedom, three dimensional bipedal robot simulation to walk. Video and more information can be found at
A realtime pattern generator for biped walking
, 2002
"... For realtime walking control of a biped robot, we analyze the dynamics of a threedimensional inverted pendulum whose motions are constrained onto an arbitrarily defined plane. This analysis leads us a simple linear dynamics, the ThreeDimensional Linear Inverted Pendulum Mode (3DLIPM). Geometric n ..."
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Cited by 30 (5 self)
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For realtime walking control of a biped robot, we analyze the dynamics of a threedimensional inverted pendulum whose motions are constrained onto an arbitrarily defined plane. This analysis leads us a simple linear dynamics, the ThreeDimensional Linear Inverted Pendulum Mode (3DLIPM). Geometric nature of trajectories under the 3DLIPM is discussed, and an algorithm for walking pattern generation is presented. Experimental results of realtime walking control of a 12 d.o.f. biped robot HRP2L using an input device such as a game pad are also shown. 1
Exploiting Natural Dynamics in the Control of a Planar Bipedal Walking Robot
 In Proceedings of the 36th Annual Allerton Conference on Communication, Control and Computing
"... Natural dynamics can be exploited in the control of bipedal walking robots: the swing leg can swing freely once started; a kneecap can be used to prevent the leg from inverting; and a compliant ankle can be used to naturally transfer the center of pressure along the foot and help in toe o#. Each of ..."
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Cited by 26 (2 self)
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Natural dynamics can be exploited in the control of bipedal walking robots: the swing leg can swing freely once started; a kneecap can be used to prevent the leg from inverting; and a compliant ankle can be used to naturally transfer the center of pressure along the foot and help in toe o#. Each of these mechanisms helps make control easier to achieve and results in motion that is smooth and natural looking. We describe a simple control algorithm using these natural mechanisms which requires very little computation. The necessary sensing consists of joint angles and velocities, body pitch and angular velocity, and ground reaction forces. Using this simple algorithm, we have controlled a seven link planar bipedal robot, called Spring Flamingo, to walk. Video, photographs, and more information on Spring Flamingo can be found at http://www.leglab.ai.mit.edu 1 Introduction A powerful practice in machine design and control is to design mechanisms which have natural dynamics that make contr...
Motion Balance Filtering
, 2000
"... This paper presents a new technique called motion balance filtering, which corrects an unbalanced motion to a balanced one while preserving the original motion characteristics as much as possible. Differently from previous approaches that deal only with the balance of static posture, we solve the ..."
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Cited by 24 (2 self)
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This paper presents a new technique called motion balance filtering, which corrects an unbalanced motion to a balanced one while preserving the original motion characteristics as much as possible. Differently from previous approaches that deal only with the balance of static posture, we solve the problem of balancing a dynamic motion. We achieve dynamic balance by analyzing and controlling the trajectory of the zero moment point (ZMP). Our algorithm consists of three steps. First, it analyzes the ZMP trajectory to find out the duration in which dynamic balance is violated. Dynamic imbalance is identified by the ZMP trajectory segments lying out of the supporting area. Next, the algorithm modifies the ZMP trajectory by projecting it into the supporting area. Finally, it generates the balanced motion that satisfies the new ZMP constraint. This process is formulated as a constrained optimization problem so that the new motion resembles the original motion as much as possible. Expe...
A sliding controller for bipedal balancing using integrated movement of contact and noncontact limbs
 Proc. International Conference on Intelligent Robots and Systems (IROS
, 2004
"... Abstract—We present an algorithm that provides enhanced flexibility and robustness in the control of singleleg humanoid standing through the coordination of stance leg ankle torques and stabilizing movements of noncontact limbs. Current control approaches generally assume the presence of explicitl ..."
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Cited by 23 (10 self)
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Abstract—We present an algorithm that provides enhanced flexibility and robustness in the control of singleleg humanoid standing through the coordination of stance leg ankle torques and stabilizing movements of noncontact limbs. Current control approaches generally assume the presence of explicitly specified joint reference trajectories or desired virtual force calculations that ignore system dynamics. Here we describe a practical controller that 1) simplifies control of abstract variables such as the center of mass location using a twostage modelbased plant linearization; 2) determines motion of noncontact limbs useful for achieving control targets while satisfying dynamic balance constraints; and 3) provides robustness to modeling error using a sliding controller. The controller is tested with a morphologically realistic, 3dimensional, 18 degreeoffreedom humanoid model serving as the plant. It is demonstrated that the controller can use less detailed control targets, and reject stronger disturbances, than previously implemented controllers that employ desired virtual forces and static body calculations. I.
Simulation of an Autonomous Biped Walking Robot Including Environmental Force Interaction
 IEEE Robotics and Automation Magazine
, 1998
"... This autonomous biped walking control system is based on the reactive force interaction at the foothold. The precise 3D (three dimensional) dynamic simulation presented includes: 1) a posture controller which accommodate the physical constraints of the reactive force/torque on the foot by quadratic ..."
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Cited by 23 (1 self)
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This autonomous biped walking control system is based on the reactive force interaction at the foothold. The precise 3D (three dimensional) dynamic simulation presented includes: 1) a posture controller which accommodate the physical constraints of the reactive force/torque on the foot by quadratic programming. 2) a realtime COM (center of mass) tracking controller for foot placement, with a discrete inverted pendulum model. 3) a 3D dynamic simulation scheme with precise contact with the environment. The proposed approach realizes the robust biped locomotion because the environmental interaction is directly controlled. The proposed method is applied to the 20 axes simulation model, and the stable biped locomotion with velocity of 0.25 m/sec and stepping time of 0.5 sec/step is realized. I. Introduction A NUMBER OF biped walking systems have been proposed in the previous works[1][12]. Since the reactive force and torque on the foothold depend on its complicated characteristics, the...
Insect designs for improved robot mobility
 Proceedings of 4 th Int. Conf. On Climbing and Walking Robots (CLAWAR), From Biology to Industrial Applications, edited by K. Berns and R. Dillmann, Professional Engineering Publishing
, 2001
"... This paper reviews work performed in the Biorobotics Lab at Case Western Reserve University. Our goal is to use intelligent biological inspiration to develop robots with mobility approaching that of legged animals. We have produced a series of robots that have mobility increasingly more similar to t ..."
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Cited by 19 (5 self)
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This paper reviews work performed in the Biorobotics Lab at Case Western Reserve University. Our goal is to use intelligent biological inspiration to develop robots with mobility approaching that of legged animals. We have produced a series of robots that have mobility increasingly more similar to that of cockroach. Some of our other projects use more simplified designs and benefit from more abstract biological principles. A new robot uses one drive motor and its gait changes passively so that it walks at high speed in a tripod gait and climbs obstacles with its legs inphase. 1