Control of hopping through active virtual tuning of leg damping for serially actuated legged robots

Secer, Gorkem; Saranlı, Uluç

doi:10.1109/icra.2014.6907524

Cited by 5 publications

(5 citation statements)

References 28 publications

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“…On the other hand, existence of damping in the leg requires energy injection to the system in order to compensate for losses. Therefore, we first consider a single linear actuator, which is serial to leg spring, as in [29,33]. Physical significance of using a linear actuator in the leg has been validated in [34] by modeling muscle activation in the leg, which injects energy to legged animals during the stance phase, with a force-free leg length actuation.…”

Section: Anchoring Slip Template To Md-slip Modelmentioning

confidence: 99%

On the periodic gait stability of a multi-actuated spring-mass hopper model via partial feedback linearization

Hamzaçebi

Morgül

2017

Nonlinear Dyn

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Spring-loaded inverted pendulum (SLIP) template (and its various derivatives) could be considered as the mostly used and widely accepted models for describing legged locomotion. Despite their simple nature, as being a simple spring-mass model in dynamics perspective, the SLIP model and its derivatives are formulated as restricted three-body problem, whose non-integrability has been proved long before. Thus, researchers proceed with approximate analytical solutions or use partial feedback linearization when numerical integration is not preferred in their analysis. The key contributions of this paper can be divided into two parts. First, we propose a dissipative SLIP model, which we call as multi-actuated dissipative SLIP (MD-SLIP), with two extended actuators: one linear actuator attached serially to the leg spring and one rotary actuator attached to hip. The second contribution of this paper is a partial feedback linearization strategy by which we can cancel some nonlinear dynamics of the proposed model and obtain exact analytical solution for the equations of motion. This allows us to investigate stability characteristics of the hopping gait obtained from the MD-SLIP model. We illustrate the applicability of our solutions with open-loop and closed-loop hopping performances on rough terrain simulations.

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Section: Anchoring Slip Template To Md-slip Modelmentioning

confidence: 99%

On the periodic gait stability of a multi-actuated spring-mass hopper model via partial feedback linearization

Hamzaçebi

Morgül

2017

Nonlinear Dyn

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“…Similarly, Approximate analytical solution † Note that subscripts represent the system parameters at critical times such as y td , y b , and y lo represent the leg position at touchdown, bottom and liftoff events, respectively. linear actuators are also used for energy regulation purposes in vertical hopping robot models [10], [11].…”

Section: Vertical Slip Model With Slider-crank Mechanism (Slip-scm)mentioning

confidence: 99%

“…1 to model energy losses due to slider-crank actuation during the compression and decompression phases. Similar leg damping definitions are also used in literature to support analytical tractability of the dynamic equations [10].…”

Section: B System Dynamicsmentioning

confidence: 99%

“…However, such actuation methods are infeasible when the horizontal speed of the COM is small and can not even satisfy a rhythmic hopping when the locomotion is constrained to the vertical direction. An ad-hoc solution for this problem is to use linear actuators in series with the compliant leg to supply additional energy to the system [10], [11]. However, it requires extensive mechanical revisions on the robot platforms and has a non-negligible effect on system dynamics even if the motor is in the idle mode.…”

Section: Introductionmentioning

confidence: 99%

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Extending the lossy Spring-Loaded Inverted Pendulum model with a slider-crank mechanism

Orhon

Odabaş

Uyanik

et al. 2015

2015 International Conference on Advanced Robotics (ICAR)

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Spring Loaded Inverted Pendulum (SLIP) model has a long history in describing running behavior in animals and humans as well as has been used as a design basis for robots capable of dynamic locomotion. Anchoring the SLIP for lossy physical systems resulted in newer models which are extended versions of original SLIP with viscous damping in the leg. However, such lossy models require an additional mechanism for pumping energy to the system to control the locomotion and to reach a limit-cycle. Some studies solved this problem by adding an actively controllable torque actuation at the hip joint and this actuation has been successively used in many robotic platforms, such as the popular RHex robot. However, hip torque actuation produces forces on the COM dominantly at forward direction with respect to ground, making height control challenging especially at slow speeds. The situation becomes more severe when the horizontal speed of the robot reaches zero, i.e. steady hoping without moving in horizontal direction, and the system reaches to singularity in which vertical degrees of freedom is completely lost. To this end, we propose an extension of the lossy SLIP model with a slider-crank mechanism, SLIP-SCM, that can generate a stable limit-cycle when the body is constrained to vertical direction. We propose an approximate analytical solution to the nonlinear system dynamics of SLIP-SCM model to characterize its behavior during the locomotion. Finally, we perform a fixed-point stability analysis on SLIP-SCM model using our approximate analytical solution and show that proposed model exhibits stable behavior in our range of interest.

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“…so long as the robot is in motion (such thatφ = 0) to maximize the instantaneous rate of change of energy in stance subject to Assumption 1 (a related 1-D controller was proposed in [23] using active damping). We call this controller the Stance Energy Injection Controller and note that it can be implemented using encoders alone for sensing and without precise knowledge of the plant other than the kinematics.…”

Section: B the Stance Energy Injection Controller: Motor Usage In Stmentioning

confidence: 99%

An empirical investigation of legged transitional maneuvers leveraging Raibert's Scissor algorithm

Duperret

Koditschek

2015

2015 IEEE International Conference on Robotics and Biomimetics (ROBIO)

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We empirically investigate the implications of applying Raibert's Scissor algorithm to the Spring Loaded Inverted Pendulum (SLIP) model in combination with other controllers to achieve transitional maneuvers. Specifically, we are interested in how the conjectured neutral stability of Raibert's algorithm allows combined controllers to push the system's operating point around the state space without needing to expend limited control affordance in overcoming its stability or compensating for its instability. We demonstrate 2 cases where this facilitates the construction of interesting transitional controllers on a physical robot. In the first we use the motors in stance to maximize the rate of change of the body energy; in the second we take advantage of the local environmental energy landscape to push the robot's operating point to a higher or lower energy level without expending valuable motor affordance. We present data bearing on the energetic performance of these approaches in executing an accelerate-and-leap maneuver on a monopedal hopping robot affixed to a boom in comparison to the cost of anchoring the robot to the SLIP template.

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Control of hopping through active virtual tuning of leg damping for serially actuated legged robots

Cited by 5 publications

References 28 publications

On the periodic gait stability of a multi-actuated spring-mass hopper model via partial feedback linearization

On the periodic gait stability of a multi-actuated spring-mass hopper model via partial feedback linearization

Extending the lossy Spring-Loaded Inverted Pendulum model with a slider-crank mechanism

An empirical investigation of legged transitional maneuvers leveraging Raibert's Scissor algorithm

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