TY - JOUR
T1 - H∞-Based Terrain Disturbance Rejection for Hydraulically Actuated Mobile Manipulators with a Nonrigid Link
AU - Rigotti-Thompson, Mattia
AU - Torres-Torriti, Miguel
AU - Auat Cheein, Fernando A.
AU - Troni, Giancarlo
N1 - Funding Information:
Manuscript received June 25, 2019; revised February 3, 2020; accepted March 9, 2020. Date of publication March 30, 2020; date of current version October 14, 2020. Recommended by Technical Editor H.-T. Yau. This work was supported by the National Commission for Science and Technology Research of Chile (Conicyt) under Fondecyt Grant 1171760, Fondequip Grant 120141, and Basal Grant FB0008. (Corresponding author: Miguel Torres-Torriti.) Mattia Rigotti-Thompson and Miguel Torres-Torriti are with the Department of Electrical Engineering, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile (e-mail: [email protected]; [email protected]).
Publisher Copyright:
© 1996-2012 IEEE.
PY - 2020/10
Y1 - 2020/10
N2 - Decoupling the end-effector motion from that of the mobile base of mobile manipulators traversing uneven terrains is important. This is especially so in mining, where material spillage from excavators and front-end loaders reduces productivity and slows down operations because of increased clean-up and maintenance times. Thus, this article proposes a strategy that relies on H∞ feedback control combined with feedforward action to improve the rejection of terrain disturbances that affect the orientation of the end-effector. The dynamic model of the mobile manipulator considers a floating base with nonpermanent contacts at each wheel, hydraulic actuators with nonlinear dynamics and a nonrigid arm. The arm flexibility is modeled as a passive spring-damper joint to account for inherent cantilever effects of real excavators and loaders. The analysis considers three different H∞ controller structures (single-input single-output (SISO) with feedforward, single-input multiple-output without feedforward, and multiple-input multiple-output without feedforward) to determine the benefits or disadvantages of employing the pitch rate of the mobile base as a feedforward control action or as an input handled by the H∞ controller and using only the end-effector actuator or also the other actuated joints of the arm. The root-mean-square error (RMSE) was reduced between 73.8%-86.0% when driving an industrial semiautonomous skid-steer loader over a ramp using the SISO H∞ controller with feedforward action. The tilt angle error was kept on average less than 0.9±0.1°. The same controller yields a reduction of the RMSE between 23.5%-38.4% and a tilt angle error smaller than 3.39± 0.07° on average when traversing over a bump. Hence, the strategy proposed to reject ground disturbances should contribute to reducing material spillage of existing autonomous machines that navigate with little operator intervention along mining galleries, but that cannot avoid disturbing material lying on the ground or the characteristic unevenness of mining terrains.
AB - Decoupling the end-effector motion from that of the mobile base of mobile manipulators traversing uneven terrains is important. This is especially so in mining, where material spillage from excavators and front-end loaders reduces productivity and slows down operations because of increased clean-up and maintenance times. Thus, this article proposes a strategy that relies on H∞ feedback control combined with feedforward action to improve the rejection of terrain disturbances that affect the orientation of the end-effector. The dynamic model of the mobile manipulator considers a floating base with nonpermanent contacts at each wheel, hydraulic actuators with nonlinear dynamics and a nonrigid arm. The arm flexibility is modeled as a passive spring-damper joint to account for inherent cantilever effects of real excavators and loaders. The analysis considers three different H∞ controller structures (single-input single-output (SISO) with feedforward, single-input multiple-output without feedforward, and multiple-input multiple-output without feedforward) to determine the benefits or disadvantages of employing the pitch rate of the mobile base as a feedforward control action or as an input handled by the H∞ controller and using only the end-effector actuator or also the other actuated joints of the arm. The root-mean-square error (RMSE) was reduced between 73.8%-86.0% when driving an industrial semiautonomous skid-steer loader over a ramp using the SISO H∞ controller with feedforward action. The tilt angle error was kept on average less than 0.9±0.1°. The same controller yields a reduction of the RMSE between 23.5%-38.4% and a tilt angle error smaller than 3.39± 0.07° on average when traversing over a bump. Hence, the strategy proposed to reject ground disturbances should contribute to reducing material spillage of existing autonomous machines that navigate with little operator intervention along mining galleries, but that cannot avoid disturbing material lying on the ground or the characteristic unevenness of mining terrains.
KW - Ground disturbance rejection
KW - H-infinity control
KW - hydraulic actuators
KW - mobile manipulator
KW - motion dynamics
UR - http://www.scopus.com/inward/record.url?scp=85094128121&partnerID=8YFLogxK
U2 - 10.1109/TMECH.2020.2983072
DO - 10.1109/TMECH.2020.2983072
M3 - Article
AN - SCOPUS:85094128121
SN - 1083-4435
VL - 25
SP - 2523
EP - 2533
JO - IEEE/ASME Transactions on Mechatronics
JF - IEEE/ASME Transactions on Mechatronics
IS - 5
ER -