Series Elastic Actuators for legged robots

  title={Series Elastic Actuators for legged robots},
  author={Jerry E. Pratt and Benjamin T. Krupp},
  booktitle={SPIE Defense + Commercial Sensing},
Series Elastic Actuators provide many benefits in force control of robots in unconstrained environments. These benefits include high force fidelity, extremely low impedance, low friction, and good force control bandwidth. Series Elastic Actuators employ a novel mechanical design architecture which goes against the common machine design principal of "stiffer is better." A compliant element is placed between the gear train and driven load to intentionally reduce the stiffness of the actuator. A… 
Design and Control of a Flexible Joint as a Hydraulic Series Elastic Actuator For Manipulation Applications
  • X. Cao, M. M. Aref, J. Mattila
  • Engineering
    2019 IEEE International Conference on Cybernetics and Intelligent Systems (CIS) and IEEE Conference on Robotics, Automation and Mechatronics (RAM)
  • 2019
The design and control architecture of SEAs in heavy-duty manipulation having hydraulic load dynamics with variable stiffness or damping of fluid flexibility, faces challenging issues of payload dynamics and compressibility of fluid with high order system.
Position-Based Impedance Control Design for a Hydraulically Actuated Series Elastic Actuator
Series elastic actuators (SEAs) have become a common actuation method in torque-controlled electric lightweight arm applications that physically interact with the environment in assembly tasks.
Control and evaluation of series elastic actuators with nonlinear rubber springs
A state observer is proposed that captures hysteretic effects exhibited by the rubber to provide an accurate estimate of actuator torque and shows improved output impedance compared to both linear springs, and comparable bandwidth to the stiff linear spring up to 1.5 Hz.
Design and Measurement Error Analysis of a Low-Friction, Lightweight Linear Series Elastic Actuator
Series elastic actuators (SEAs) have many benefits for force controlled robotic applications. Placing an elastic member in series with a rigid actuator output enables more-stable force control and
Design and Control Considerations for High-Performance Series Elastic Actuators
This paper discusses design and control of a prismatic series elastic actuator with high mechanical power output in a small and lightweight form factor. A design is introduced that pushes the
Impedance Control of Hydraulic Series Elastic Actuator with a Model-Based Control Design
A novel subsystem-dynamics-based controller for an HSEA is designed using the virtual decomposition control (VDC) approach as a framework and is incorporated as an inner-loop controller for previously designed a novel impedance controller.
Design of a Compact, Lightweight, Electromechanical Linear Series Elastic Actuator
Series Elastic Actuators (SEAs) have several benefits for force controlled robotic applications. Typical SEAs place an elastic element between the motor and the load, increasing shock tolerance,
A power autonomous monopedal robot
We present the design and initial results of a power-autonomous planar monopedal robot. The robot is a gasoline powered, two degree of freedom robot that runs in a circle, constrained by a boom. The
Mechanical design and force control algorithm for a robot leg with hydraulic series-elastic actuators
This article presents a mechanical design structure for hydraulic actuators using the principle of series-elastic actuator, considering the restriction of mechanical structure, weight and size, as
Synthesis and Design of a Bimodal Rotary Series Elastic Actuator
A novel rotary series elastic actuator (RSEA) with a two-mode, or bimodal, elastic element was designed and tested. This device was developed to eliminate the compromise between human safety and


Series elastic actuator development for a biomimetic walking robot
Series elastic actuators have linear springs intentionally placed in series between the motor and actuator output. The spring strain is measured to get an accurate estimate of force. A second order
Series elastic actuators
  • G. Pratt, M. Williamson
  • Engineering
    Proceedings 1995 IEEE/RSJ International Conference on Intelligent Robots and Systems. Human Robot Interaction and Cooperative Robots
  • 1995
It is proposed that for natural tasks, zero motion force bandwidth isn't everything, and incorporating series elasticity as a purposeful element within the actuator is a good idea.
Stiffness Isn't Everything
This paper proposes that for natural tasks where small-motion bandwidth is not of paramount concern, actuator to load interfaces should be significantly less stiff than in most present designs.
Virtual actuator control
A control method in which the real joint actuators are used to mimic virtual actuators which can be more intuitive and hence make the control problem more straightforward is presented.
Exploiting Natural Dynamics in the Control of a Planar Bipedal Walking Robot
A simple control algorithm is described using natural dynamics to control a seven link planar bipedal robot, called Spring Flamingo, to walk and results in motion that is smooth and natural looking.
Exploiting Natural Dynamics in the Control of a 3 D Bipedal Walking Simulation
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
Virtual model control of a bipedal walking robot
A control scheme called virtual model control, a motion control language that uses simulations of imagined mechanical components to create forces, which are applied through real joint torques, thereby creating the illusion that the virtual components are connected to the robot.
Intuitive control of a planar bipedal walking robot
  • J. Pratt, G. Pratt
  • Computer Science
    Proceedings. 1998 IEEE International Conference on Robotics and Automation (Cat. No.98CH36146)
  • 1998
This work has compelled a seven link planar bipedal robot, called Spring Flamingo, to walk, which walks both slowly and quickly, walks over moderate obstacles, starts, and stops.
The RoboKnee: an exoskeleton for enhancing strength and endurance during walking
The RoboKnee allows the wearer to climb stairs and perform deep knee bends while carrying a significant load in a backpack, and provides most of the energy required to work against gravity while the user stays in control, deciding when and where to walk.
Proceedings of ISER
  • Proceedings of ISER
  • 1995