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Rob Gorbet

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9 papers
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9

IROS Conference 2021 Conference Paper

Memory-based Deep Reinforcement Learning for POMDPs

  • Lingheng Meng
  • Rob Gorbet
  • Dana Kulic

A promising characteristic of Deep Reinforcement Learning (DRL) is its capability to learn optimal policy in an end-to-end manner without relying on feature engineering. However, most approaches assume a fully observable state space, i. e. fully observable Markov Decision Processes (MDPs). In real-world robotics, this assumption is unpractical, because of issues such as sensor sensitivity limitations and sensor noise, and the lack of knowledge about whether the observation design is complete or not. These scenarios lead to Partially Observable MDPs (POMDPs). In this paper, we propose Long-Short-Term-Memory-based Twin Delayed Deep Deterministic Policy Gradient (LSTM-TD3) by introducing a memory component to TD3, and compare its performance with other DRL algorithms in both MDPs and POMDPs. Our results demonstrate the significant advantages of the memory component in addressing POMDPs, including the ability to handle missing and noisy observation data.

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ICRA Conference 2018 Conference Paper

Spherical Foot Placement Estimator for Humanoid Balance Control and Recovery

  • Brandon J. DeHart
  • Rob Gorbet
  • Dana Kulic

One of the main challenges of bipedal gait is to avoid falling due to unknown disturbances. Compensating for these disturbances in bipeds is often achieved by leaning or stepping. In this work, the Spherical Foot Placement Estimator (SFPE) is introduced, which uses the biped's current kinematics and dynamics to predict if a step is needed, and if so where to step, to restore balance in 3D. An example of a controller using the SFPE is shown, which augments an existing optimal controller with both leaning and stepping: SFPE-based feedback is used to generate a desired momentum for momentum-based leaning while the SFPE point is used as a control reference for stepping. The new estimator outperforms existing balance criteria by providing both recovery step location prediction and momentum objectives with smooth dynamics.

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IROS Conference 2015 Conference Paper

Control of soft pneumatic finger-like actuators for affective motion generation

  • Mohammadreza Memarian
  • Rob Gorbet
  • Dana Kulic

This paper investigates the design and implementation of a finger-like robotic structure capable of reproducing human hand gestural movements performed by a multi-fingered, hand-like structure. In this work, we present a pneumatic circuit and a closed-loop controller for a finger-like soft pneumatic actuator. Experimental results demonstrate the performance of the pneumatic and control systems of the soft pneumatic actuator, and its ability to track human movement trajectories with affective content.

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IROS Conference 2015 Conference Paper

Curiosity-Based Learning Algorithm for distributed interactive sculptural systems

  • Matthew T. K. Chan
  • Rob Gorbet
  • Philip Beesley
  • Dana Kulic

The ability to engage human observers is a key requirement for both social robots and the arts. In this paper, we propose an approach for adapting the Intelligent Adaptive Curiosity learning algorithm to distributed interactive sculptural systems. This Curiosity-Based Learning Algorithm (CBLA) allows the system to learn about its own mechanisms and its surroundings through self-experimentation and interaction. A novel formulation using multiple agents as learning subsets of the system that communicate through shared input variables enables us to scale to a much larger system with diverse types of sensors and actuators. Experiments on a prototype interactive sculpture demonstrate the exploratory patterns of the CBLA and collective learning behaviours through the integration of multiple learning agents.

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IROS Conference 2015 Conference Paper

Modelling and experimental analysis of a novel design for soft pneumatic artificial muscles

  • Mohammadreza Memarian
  • Rob Gorbet
  • Dana Kulic

Soft pneumatic artificial muscles (SPAMs) are a type of pneumatic actuator that provide customizable motion trajectories in three dimensional space without the need for rigid links or a transmission mechanism. This paper presents a novel design for producing SPAMs, named wrapped SPAMs (WSPAMs). Unlike previous SPAM designs, the production process of WSPAM is highly repeatable, while the motion trajectory can be easily modified. A model for predicting the steady-state angular displacement of a WSPAM actuator based on its geometrical parameters and the elasticity of the materials used in its production is presented and experimentally validated.

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ICRA Conference 1998 Conference Paper

Preisach Model Identification of a Two-Wire SMA Actuator

  • Rob Gorbet
  • David W. L. Wang
  • Kirsten A. Morris

In recent years, the Preisach hysteresis model (1935) has emerged as the model of choice for the behaviour of many smart materials, such as shape memory alloys (SMA). This research treats the identification of Preisach models for a differential SMA actuator. The traditional identification technique is applied, and several models are derived for the actuator. It is seen that the classical Preisach model is able to model its behaviour. However, the results raise questions concerning the robustness of the traditional identification technique, as well as the conservative nature of current passivity-based control results for the Preisach model.

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ICRA Conference 1997 Conference Paper

Stability of control for the Preisach hysteresis model

  • Rob Gorbet
  • Kirsten A. Morris
  • David W. L. Wang

The motivation for this research arises from interest in actuators made from "smart materials" such as shape memory alloys and piezoceramics. One common characteristic among these new materials is that they exhibit complex hysteresis nonlinearities. The input-output nature of the Preisach model of hysteresis results in a simple model for which identification strategies are known, and implementation is straightforward both in simulation and real-time control. This paper examines the passivity of the Preisach model, and the stability of velocity feedback control for hysteretic actuators.

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ICRA Conference 1995 Conference Paper

General Stability Criteria for a Shape Memory Alloy Position Control System

  • Rob Gorbet
  • David W. L. Wang

This paper deals with the L/sub 2/ stability of a shape memory alloy actuated position control system, based on a single wire under constant axial load. Presuming a controller has certain specific dissipativity characteristics, it is shown that system stability can be guaranteed for a large class of controllers. In particular, the results can be used to show stability under approximated PID, PI and PD control. The result is used to find a stabilizing PI controller, and the corresponding experimental data is shown.

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ICRA Conference 1995 Conference Paper

Improving the Response of SMA Actuators

  • R. Andrew Russell
  • Rob Gorbet

Shape memory alloy (SMA) based actuators have a number of attributes which make them useful for robotic applications. Unfortunately their response is relatively slow being limited by the speed with which the SMA can be heated and cooled. This paper describes two novel developments of the basic SMA actuator which improve dynamic performance. To allow rapid heating of the shape memory alloy wire without the danger of over heating an infrared temperature sensor is introduced. Cooling is improved with the aid of a mobile heat sink. These developments are described and preliminary results are presented.

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