Null-space impedance control with disturbance observer

In the paper, a method for the estimation of the contact force and contact location is proposed. Contact can occur at any point on the body of the robot manipulator. The contact force estimation algorithm is based on the measurement of the part of the joint torques caused by the external force. As this is a complex nonlinear problem, the proposed method is based on nonlinear constrained optimization. Using certain assumptions, the complexity of the problem is reduced. In this paper, only robots with cylindrically-shaped links are considered. The simulation and experimental results show that the proposed approach allows the estimation of the contact forces by using only the joint torque sensors, without any additional external sensory systems for the detection of contacts along the robot body-structure.

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“…The external force was modelled as given by Eq. (12). The simulation results can be seen in Figure 12.…”

Section: Experimental Evaluation Of the Contact Point Detection Algormentioning

confidence: 99%

External Joint Torque-Based Estimation of Contact Information

Likar

Žlajpah

2014

International Journal of Advanced Robotic Systems

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“…However, in practice the parameters of the dynamic model are not known exactly, and also joint accelerations can not be measured directly. To overcome these problems, the external joint torques can be estimated using disturbance observers or momentum based observers [11], [12], which are out of the scope of this paper. In the paper we assume, that the external torques obtained using the dynamic model and the external torques from the robot sensors are suitable enough to be used in the process of contact estimation.…”

Section: A External Joint Torquesmentioning

confidence: 99%

Estimation of contact information using nonlinear optimization

Likar

Žlajpah

2014

2014 23rd International Conference on Robotics in Alpe-Adria-Danube Region (RAAD)

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The paper presents an algorithm for estimating the contact information i.e. the contact force and the contact location. The estimation algorithm is based on the measurement of the part of joint torques which are caused by the external force. This torques may arise from a wide variety of contact situations, which makes this a complex nonlinear problem. Using some approximations, the complexity of the estimation problem is reduced and solved by the proposed algorithm based on nonlinear constrained optimization. In this paper only the robots with cylindrically shaped links are considered. The simulation and experimental results show that the proposed approach allows estimation of contact forces by using only joint torque sensors without any additional external sensory systems for detection of contacts along the robot body structure.

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“…Substituting N 1Ṅ 1 = −N 1J † 1 J 1 and using equalityJ 1 J † 1 = − J 1J † 1 give null space vector in (28). Recently, Nakanishi et al 15 tried to find an intuition behind this, rather complex, null space vector.…”

Section: Stability Analysismentioning

confidence: 99%

“…Equations (37) and (39) show that in the absence of external torque information, by proper choice of impedance matrices and desired rest configuration, a satisfactory compliance behavior in the null space can be achieved. Indeed, there is an error on the main task during interaction, which can be tolerated by using high gain for the main task control or a disturbance observer 28 while giving high compliance to the null space through impedance matrices. The snapshot of the system is depicted in Fig.…”

Section: Case Study IImentioning

confidence: 99%

Dynamic multi-priority control in redundant robotic systems

Sadeghian

Villani²,

Keshmiri

et al. 2013

Robotica

Self Cite

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This paper presents a dynamic-level control algorithm to meet simultaneously multiple desired tasks based on allocated priorities for redundant robotic systems. It is shown that this algorithm can be treated as a general framework to achieve control over the whole body of the robot. The control law is an extension of the well-known acceleration-based control to the redundant robots, and considers also possible interactions with the environment occurring at any point of the robot body. The stability of this algorithm is shown and some of the previously developed results are formulated using this approach. To handle the interaction on robot body, null space impedance control is developed within the multi-priority framework. The effectiveness of the proposed approaches is evaluated by means of computer simulation

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Null-space impedance control with disturbance observer

Cited by 33 publications

References 18 publications

External Joint Torque-Based Estimation of Contact Information

External Joint Torque-Based Estimation of Contact Information

Estimation of contact information using nonlinear optimization

Dynamic multi-priority control in redundant robotic systems

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