Finite-Time Fault-Tolerant Control for a Robot Manipulator Based on Synchronous Terminal Sliding Mode Control

Round 1

Reviewer 1 Report

Dear Authors,

Thank you for sharing this interesting proposal.

To reduce the effect of picking a phenomenon associated with the AFTC strategy, this paper used the finite-time synchronization technique in a fault-tolerant controller for a serial robot manipulator. Due to the ability to simultaneously approach zero of each joint, this technique can quickly respond to faults before the controller gets information from the estimation process. Two proposed controllers were verified in simulation and real robot system. Depend on the knowledge of each system, the advantages and disadvantages of the two proposed have been shown. Some comments give follow as:

1) Please drawing the block diagram in the introduction regarding your proposed method and explain about sub-blocks step-by-step.

2) The authors used active FTC, so how you diagnosis the robot faults?

3) Please add one paragraph in the introduction due to contribution and explain it clearly.
4) Adjustment synchronization parameters in (11) can be said that it is one important part of this paper. How authors can select those parameters?
5) In a real implementation, the feedback information of fault was used from an extended state observer. However, this signal usually included noise and chattering due to the occurrence of the torque input term. How authors can reduce those effects and apply them in the real robot system?
6) In implementation results, the authors used the threshold to detected faults. What is the advantage and disadvantage of this technique? Is it necessary in this paper? Because the lumped of uncertainties, disturbances and faults were compensated in a controller of active fault-tolerant strategy.
7) In subsection 4.2 (line 204 to 211), “synchronous fast terminal” should be “synchronous terminal”.

Regards

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors deal with two types of manipulator control. The topic as well as content of the paper are interesting.The introduction is well written. In general, the paper has acceptable content, however it need to be revised. There are several issues which should be corrected / complete.

1. Equation (1): There is error in mathematical description. The centripetal and Coriolis has wrong written domain.
2. Equation (1): You only write Ff(dq/dt) - friction term. What kind of friction model do you assume ?
3. In comments after Equation (1) are several issues: "and the gravitation force" - it is not force but vector of gravitational force, "friction term" - it is what ? Matrix ? Vector ? need to be clearly defined. Tau is not torque, but also vector of torques.
4. Equations: All matrices and vectors should be written as bold without italic. Correct the Equation (1).
5. After Equation (5) there is no description of parameters from Definition. It would be suitable to comment this definition.
6. Equation (14): is it your own relation or it is based on previous works ?If it is your own contribution, you should describe it. Why this term ?
7. Equation (32): Do you control only joints revolution ? What about joints velocity and acceleration ? Do you have any restrictions to these kinematic parameters?
8. After Equation (36) you write about setup parameters. What is the key to choose the values just like that ? Is it based on real parameters?
9. You deal with MATLAB simulation. This simulation should be described in details. For example how you get your dynamic model ? Analytically? Numerically? IS it for real-time application? etc.
10. 6.1 Experimental setup: there is an error, Fig. 9 does not exist. 
11. The simulation and experimental results should be set with the same parameters and compare them. For example desired trajectory described by equation (39) is different in comparisson with trajectory from Equation (32).
12. How did you measure parameters shown in the Fig. 6 and Fig. 7? Experiments as well as simulations have to be described in more details.
13. The conclusion is very poor. The contributions of the paper have to be emphasized and described in more details.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear Authors,

Thank you for your cover letter. Regarding the second round review, the manuscript can be suitable for publishing in this journal.

Good-Luck for your future research^^.

Regards