## 5 Conclusions  
In this paper, our goal was to design ground test equipment with active-suspension gravity compensation for space manipulators. The approach proposed in this paper can be applied in ground gravity compensation requirements of space manipulators and other space equipment. To achieve this, we designed an intelligent controller that implements 3 degrees of freedom of active-suspension gravity compensation. The controller was tuned using the ADP method, and the parameters were fine-tuned based on the actual operating conditions. To improve control accuracy and solve the execution lag problem found during the actual testing, we used four methods mentioned in the paper. The designed controller can be used in other similar controller design requirements, and the protective measures in our controller can prevent safety issues during the initial debugging. When the controller is applied in a new environment, its control parameters need to be retuned according to the actual situation. For the lag compensation method proposed by us, it should satisfy two conditions when applied to other control systems. First, the input of the system should be measurable, and second, the controller of the system should be able to adapt to the disturbance brought by lag compensation. The essence of this lag compensation is to mix the controller inputs calculated from the current control cycle and the previous control cycle and the measured controller inputs in a certain proportion as the controller input for the current cycle. In the system described in this paper, the lag time is approximately four control  
Figure 14: Performance during 200 ms. (**a**) Inputs \(\mathrm{v_{yb}}\) in blue and \(\mathrm{v_{ybmes}}\) in purple without method 4. (**b**) Inputs \(\mathrm{v_{yb}}\) in blue and \(\mathrm{v_{ybmes}}\) in purple with method 4. (**c**) Output F in red without method 4. (**d**) Output F in red with method 4.  
cycles, and our compensation method can effectively suppress the control oscillation caused by this lag. The application scope of this lag compensation method can be studied further. In the paper, we conducted a simulation of a complete application of the system, and the simulation results were close to the actual results, indicating that our intelligent controller can achieve our control goals and complete the control requirements of the ground test equipment for active-suspension gravity compensation of a space manipulator. With the assistance of this system, space manipulators can be tested in a ground environment, which facilitates the study of motion characteristics of space manipulators by researchers. In actual use, our test equipment has successfully assisted a space manipulator in completing ground deployment tests, with stable operation.  
Conceptualization, Z.J. and X.Z.; methodology, X.Z.; software, X.Z.; validation, Z.Z., Y.L. and Y.H.; formal analysis, Z.Z.; investigation, Z.X.; resources, Z.X.; data curation, Z.Z.; writing--original draft preparation, X.Z.; writing--review and editing, Z.J. and X.Z.; visualization, X.Z. and Y.L.; supervision, Z.X. and Y.H.; project administration, Z.J. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
Not available.  
The authors declare no conflict of interest.