### Abstract

Implementation of a task using a redundant robot arm requires a solution of the inverse differential kinematic problem. Previous algorithms for this problem used various optimized objective functions to limit null space motion. The problem with using an objective function is that the weight needs to be adjusted according to the type of operation. Since the order of the objective function is lower than that of the kinematic constraints using a pseudo inverse, it is hard to predict null space motion for a repetitive task. This type of problem is said to be manually controlled by the objective function. In this study, we introduce a matrix augmentation method so that active control of the null space motion can be implemented. We use the normal vector of the plane defined by the wrist, elbow and shoulder points and the reference vector P_{w}-P_{s} as the control criterion, and we define the output angle between these two vectors. In addition, the saturation method is used to prevent violation of the joint angle limit constraints. A simulation and an experiment using a 7-DOF robot arm were carried out to verify the performance of the proposed algorithm. For the simulation, we used Matlab to generate the null space motion, and we used a 7-DOF robot arm developed in our lab to verify the proposed method experimentally. The proposed algorithm allows redundancy resolution, since intuitive and predictable null space motion can be generated according to a desired output angle.

Original language | English |
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Title of host publication | MOVIC 2014 - 12th International Conference on Motion and Vibration Control |

Publisher | Japan Society of Mechanical Engineers |

Publication status | Published - 2014 |

Event | 12th International Conference on Motion and Vibration Control, MOVIC 2014 - Sapporo, Hokkaido, Japan Duration: 2014 Aug 3 → 2014 Aug 7 |

### Other

Other | 12th International Conference on Motion and Vibration Control, MOVIC 2014 |
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Country | Japan |

City | Sapporo, Hokkaido |

Period | 14/8/3 → 14/8/7 |

### Fingerprint

### Keywords

- Matrix augmentation
- Null-space motion control
- Objective function
- Output angle
- Redundant robot arm
- Saturation method

### ASJC Scopus subject areas

- Control and Systems Engineering

### Cite this

*MOVIC 2014 - 12th International Conference on Motion and Vibration Control*Japan Society of Mechanical Engineers.

**Null space motion control of a redundant robot arm using matrix augmentation and saturation method.** / Cho, Hyun Cheol; Song, Jae-Bok.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

*MOVIC 2014 - 12th International Conference on Motion and Vibration Control.*Japan Society of Mechanical Engineers, 12th International Conference on Motion and Vibration Control, MOVIC 2014, Sapporo, Hokkaido, Japan, 14/8/3.

}

TY - GEN

T1 - Null space motion control of a redundant robot arm using matrix augmentation and saturation method

AU - Cho, Hyun Cheol

AU - Song, Jae-Bok

PY - 2014

Y1 - 2014

N2 - Implementation of a task using a redundant robot arm requires a solution of the inverse differential kinematic problem. Previous algorithms for this problem used various optimized objective functions to limit null space motion. The problem with using an objective function is that the weight needs to be adjusted according to the type of operation. Since the order of the objective function is lower than that of the kinematic constraints using a pseudo inverse, it is hard to predict null space motion for a repetitive task. This type of problem is said to be manually controlled by the objective function. In this study, we introduce a matrix augmentation method so that active control of the null space motion can be implemented. We use the normal vector of the plane defined by the wrist, elbow and shoulder points and the reference vector Pw-Ps as the control criterion, and we define the output angle between these two vectors. In addition, the saturation method is used to prevent violation of the joint angle limit constraints. A simulation and an experiment using a 7-DOF robot arm were carried out to verify the performance of the proposed algorithm. For the simulation, we used Matlab to generate the null space motion, and we used a 7-DOF robot arm developed in our lab to verify the proposed method experimentally. The proposed algorithm allows redundancy resolution, since intuitive and predictable null space motion can be generated according to a desired output angle.

AB - Implementation of a task using a redundant robot arm requires a solution of the inverse differential kinematic problem. Previous algorithms for this problem used various optimized objective functions to limit null space motion. The problem with using an objective function is that the weight needs to be adjusted according to the type of operation. Since the order of the objective function is lower than that of the kinematic constraints using a pseudo inverse, it is hard to predict null space motion for a repetitive task. This type of problem is said to be manually controlled by the objective function. In this study, we introduce a matrix augmentation method so that active control of the null space motion can be implemented. We use the normal vector of the plane defined by the wrist, elbow and shoulder points and the reference vector Pw-Ps as the control criterion, and we define the output angle between these two vectors. In addition, the saturation method is used to prevent violation of the joint angle limit constraints. A simulation and an experiment using a 7-DOF robot arm were carried out to verify the performance of the proposed algorithm. For the simulation, we used Matlab to generate the null space motion, and we used a 7-DOF robot arm developed in our lab to verify the proposed method experimentally. The proposed algorithm allows redundancy resolution, since intuitive and predictable null space motion can be generated according to a desired output angle.

KW - Matrix augmentation

KW - Null-space motion control

KW - Objective function

KW - Output angle

KW - Redundant robot arm

KW - Saturation method

UR - http://www.scopus.com/inward/record.url?scp=84925352888&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84925352888&partnerID=8YFLogxK

M3 - Conference contribution

AN - SCOPUS:84925352888

BT - MOVIC 2014 - 12th International Conference on Motion and Vibration Control

PB - Japan Society of Mechanical Engineers

ER -