## 1 Introduction
A joint optimization method, based on a multi-objective response surface approximation model and a finite element simulation program, was proposed to realize the lightweight optimization of new-energy vehicle frames. As a result, the weight of the frame was reduced from 25.05 kg to 19.86 kg, a weight reduction of 20.7%, achieving a significant weight reduction effect. Moreover, mass reduction (metal economy) is also part of our garbage truck frame optimization steps, so this paper correlates with our research goals. The center of gravity (COG) influence on the frame strength is an actual question in our case, taking into account the fact that the compactor position in a garbage truck is variable, which is why it is recommended to research the results in paper [7]. In paper [8], the authors proposed the basic theory of structural reliability combined with bus driving characteristics, the concept of strength reliability for bus body frames, and a calculation method based on the Monte Carlo method. Study [9], on the battery management system for electric garbage compactor trucks, highlights that the battery mass and configuration significantly impact system stability, making proper estimation of the state-of-charge (SoC) and state-of-health (SoH) critical for managing the battery load distribution and center of gravity. A frequent aspect related to the boundary conditions of garbage truck loads is associated with compactor mounting brackets. The topic of bracket strength is considered in several studies in regard to the example of a truck frame (as a part of it) [10,11]. In addition, the results in paper [10] indicate that suspension supports experience high levels of stress in six operating conditions and the most dangerous location of the frame always lies at the weld bead between the suspension support and the frame. The primary and secondary stress intensity, along the most dangerous path, decreased by 16.69% in the condition involving a free-hanging left front wheel and by 59.91% in the condition involving a free-hanging right rear wheel. Study [12] examined a 6 ton truck frame, modeled and analyzed using FEA, which showed that the truck frame's structural strength exceeded the load requirements, allowing for an 8.4% weight reduction, while maintaining the strength of the frame, with the maximum stress reduced from 207.3 MPa to 177.86 MPa. Stress analysis and a strength test involving a 2500 fracturing truck frame is presented in [13]. Japanese garbage truck drivers experience whole-body vibrations, which is linked to lower back pain, and a field study [14] found that diesel truck operations should be limited to 2.5 h per day in current conditions to reduce health risks. Taking into account the transition to electric traction, the issues related to theoretical low-frequency vibrations by a diesel engine have been solved in regard to the electric garbage truck being studied in this article. At the same time, the topic related to the oscillation of batteries, with large masses and a high COG, is an actual issue for future research. Yield strength is the key indicator that defines the safety factor of the frame; this topic is raised in paper [15], where the authors investigate the improvement to the fatigue strength of a high-strength hot-rolled steel sheet for use in a truck frame. Continuing on the topic of yield strength, publication [16] is dedicated to determining the features of the stressed state in terms of a passenger car frame made using an energy-absorbing material in the girder beam. Paper [17] utilizes finite element theory and a simplified model to assess the static strength and reliability of a touring car's frame structure. A finite element model was established to numerically predict the reliability of the structure's static strength in four frequently encountered operational scenarios, namely bending, torsion, braking, and turning.