# Resilient Consensus Control for Multi-Agent Systems: A Comparative Survey
## 3 Resilient Control for MASs
### DoS Attack
[38] does not require each agent to continuously broadcast its own control input and state quantity, which well maintains their own information privacy. In addition, the communication and the update of the state value can only be carried out when the state of the topological edge meets the triggering function, compared with the continuous information transmission and reception required in [30] to calculate the state observation value of the neighbor and its own real state value. Thus, the former obviously reduces the communication cost and calculation complexity, but the corresponding parameter design is much more difficult. Moreover, compared to the general state consensus realized in [30], ref. [38] can achieve more accurate consensus results as exponential consensus. Based on the information of the Laplace matrix eigenvalues of the communication topology, the control scheme designs the trigger parameter \(\beta_{ij}\) in the normal communication scenario, and then, achieves the state consensus of the system. In the case that the communication situation is under DoS attack, it can be shown that when the DoS attack frequency and the attack duration satisfy the inequality condition (related to the sleep time of DoS attack), the controller (17) can mitigate the communication anomaly caused by the DoS attack and achieve the security consensus of the system. Meanwhile, the design of parameters in both the controller (17) and the trigger function (18) relies on global information such as the non-zero minimum eigenvalue of the Laplace matrix. Thus, it is not a fully distributed control structure. Considering the periodic DoS attack, ref. [48] models the error dynamics of the MASs as a switched time-varying delay system and proposes an event-triggered mechanism control protocol using the input time delay method, finally achieving the exponential consensus of the system. Its highlight is that, based on the existing theoretical research of time delay MASs, it converts the sampled-data term into a time delay term in the system. In addition, according to the sleep time of different DoS attacks, ref. [48] also puts forward an optimization algorithm to select the control parameters of the distributed event-triggered protocol. However, the attack is required to occur periodically. Meanwhile, the exact value of attack cycles and sleep time need to be known in advance, which makes [48] less applicable. To sum up, for the resilient consensus problem under DoS attack, the current control scheme with high feasibility is to use the observer to simulate the evolution of normal state values during the communication paralysis period and combine the asynchronous triggered scheme to achieve consensus under the premise of limiting the attack frequency and duration. According to the accuracy and complexity of the observer and the sensitivity of the triggered mechanism, the conservatism and practicality of the corresponding consensus conclusions are different. To improve the practicability of the conclusion, the key lies in whether the attack model can fully ensure the accuracy of the prediction of the attacked object and the reduction of the actual damage. In order to give a clear survey, we summarize the relevant work in Table 2 according to DoS type, centralized, scalability, results and references.