How to ensure the reducer "moving" but not "vibration"

The vibration problem of the reducer has always been a pain point in the application of robots. It not only affects the physical examination of the end users of robots, but also, more importantly, limits the robot's ability to "show its feet" in the field of high-end equipment manufacturing. Because the vibration of the reducer will be transmitted to the end of the robot, so that the end of the jitter, greatly reduce the trajectory accuracy of the robot, repeated positioning accuracy.

For example, when the robot is welding complex surfaces and cutting complex shapes, the motion trajectory of the robot will not be smooth or even discontinuous due to the vibration of the reducer, which is not conducive to the optimization of the robot trajectory. It can be said that if the vibration problem of the reducer can not be effectively solved, the robot will not be able to undertake similar high-speed and high-precision production tasks.

Not only that, once the reducer vibration is too large, the upper limit of the robot joint motion speed will be greatly reduced, and the positioning time will be increased, thus affecting the efficiency of the robot; The vibration of the reducer will also make the robot produce additional impact force in the process of movement, thus reducing the service life of the whole system.

What causes the vibration of the reducer?

So how can we solve this headache reducer vibration problem?

We first need to start from the principle, to understand why the reducer will produce vibration. Taking the harmonic reducer as an example, from the point of view of the gear meshing principle, when the meshing interference or the tooth surface finish is poor, the meshing impact force will increase, which will cause the vibration of the reducer to increase sharply.

From the perspective of thin-walled cylinder mechanism, the deep-seated causes of harmonic reducer vibration are as follows:

Through theoretical research, the vibration size of reducer is proportional to the density of the material, and inversely proportional to the Young's modulus and Poisson's ratio of the material.

The influence of the structure design on the vibration of the reducer, the size of the vibration is inversely proportional to the meshing length of the gear teeth, inversely proportional to the wall thickness of the flexible wheel, and proportional to the radius of the flexible wheel.

Relationship between vibration amplitude and tooth meshing length of harmonic reducer

Relationship between vibration amplitude of harmonic reducer and flexwheel wall thickness

Relationship between vibration amplitude of harmonic reducer and flexwheel wall thickness

The influence of machining accuracy of parts, some key parts in the reducer, such as the influence of camshaft shape and position tolerance tooth surface finish, if the coaxiality and symmetry of the shape and position tolerance is large, the harmonic reducer will produce eccentricity, eccentricity will become an incentive of the reducer vibration, thereby exacerbating the vibration.

The impact of reducer assembly, the unreasonable selection of parts, not only will make the reducer system unbalanced force, but also will produce new harmonic frequency, which will not only make the system vibration increase, at the same time increase the probability of resonance of the system.

Reducer vibration solution

Based on the research of the above vibration theory, Haozhi Electromechanical forward design and development of SP tooth profile and convex profile curve in the aspect of tooth profile and structure design, and optimize the best meshing length of tooth and the best wall thickness of flexible wheel.

In addition, the gear machining accuracy grade and tooth surface finish are improved, and the friction-lifting drive smoothness is reduced.

In terms of material selection, Haozhi chooses a new alloy steel with small density and large elastic modulus. Through continuous improvement of processing technology, the grain of the material is refined, so as to further improve the elastic modulus and Poisson's ratio of the material. These measures have well avoided excessive vibration of the reducer. The following figure is the metallographic diagram of the material grain after the improvement of the process, and its grain size grade has reached 1-2 level.

Sample edge 500X

In the aspect of parts processing, through the improvement of clamping tooling and process flow, as far as possible to reduce the parts in the processing of clamping times and the replacement of processing benchmarks, so as to improve the machining accuracy level of parts; Taking the camshaft as an example, the CAM symmetry is strictly controlled within 5μm, and the contour is less than 2μm.

In terms of assembly rules, the artificial intelligence algorithm is introduced into the assembly of harmonic reducer, and the "intelligent" matching of parts is really achieved. The flow chart of intelligent matching is as follows:

Reducer vibration improvement effect

From the comparison of the spectrum analysis diagram, it can be found that the amplitude of the improved vibration is significantly reduced. In addition, the meshing frequency and side frequency of the gear are significantly reduced, which indicates that the gear meshing state of Haozhi electromechanical reducer is good and the impact during operation is small.