In our previous work, we designed a new joint system for humanoid sized robot. This system consists of a servomotor, a harmonic drive and a link unit. This link unit includes three components; ...polymer bushes, a metal cam plate and a metal camshaft. However elastic deformation of all-polymer bushes can cause a large backlash in the system. In the present work, a new bush was developed and its fatigue behavior was investigated.
In biped walking humanoid robot, toughness, durability and lightweight of joint parts are crucial factors due to parts’ constant exposure to high torque and loads. Such ergonomically challenging ...conditions create the need for joint systems comprising independent elements capable of keeping the component operable for long periods of time. In our work, we focused on wear and thermal deformation in two different grades of both poly-ether-ether-ketone (PEEK) and polyoxymethylene (POM) plastic bushes. The components used for investigation were bushes typically employed in speed reduction devices in joint models for biped walking humanoid robots. In such joint systems, plastic bushes are directly connected to a crankshaft, playing an important role in the robot's movement ability. In order to acquire the knowledge of how to build more efficient systems, the influence of the titanium crankshaft roughness on the frictional heat occurring between the shaft and the polymer bush as well as the input axis-output axis backlash require close examination. Based on Rolling Contact Fatigue test, we established the optimal machining conditions for the crank shafts and bushes. Also, superior to other tested polymers as far as glass transition temperature, wear toughness and thermal deformation are concerned, PEEK was found to be the best suiting material for our investigation.
Reciprocating fatigue tests were performed for three kinds of samples, induction-heated 13Cr-2Ni-2Mo stainless steel, hard chromium plated and softnitrided SUS304 steels. Microstructure, wear track ...depth and hardness distribution in these materials were observed. It is concluded that the 13Cr-2Ni-2Mo stainless steel was successfully heat treated and had high wear resistance.
In our recent work, in order to realize joint element in lightweight and compact joints for tall humanoid robots, a new joint element was designed. It consists of a harmonic drive gearing device, a ...multi axis mechanism and a resin bush. The resin bush slides on a titanium crankshaft of the pole shape while the joint works. However, the bush was stuck, and stopped movement of the joint. In our present work, we observed the bush surfaces against two materials; the titanium and the 7075 aluminum alloy have been used. We could observe the differences between the titanium and the 7075 aluminum alloy by an optical microscope after the fatigue tests.
n order to establish the application possibilities in transmission parts in humanoid robot joints, wear of reinforced poly-ether-ether-ketone (PEEK) polymer bushes in friction against 7075 aluminium ...alloy cam plates is investigated. Additionally the transmission error (backlash) in robot joint was measured. The PEEK bush wear requires close examination as well as the input axis-output axis transmission error. Fatigue wear tests were performed on bushes under middle load at 3000 rpm motor speeds, while the cam plate oscillated in the humanoid robot leg joint evaluation system under 1300 kgfcm (132 Nm) load torque. The robot joint using PEEK bush achieved stable small backlash due to good friction perforance.
A newly developed single-ball RCF testing machine was used in order to investigate crack initiation direction within SUJ2. From empirical data, it was found that the distribution of crack initiation ...direction at N = 1.0x106 cycles is very close to that at N = 1.0x107. This means that the cracks that do not cause failure stop growing by 1.0x106 cycles. Some cracks however continue to grow towards the surface, at an angle of 135 degrees.
Due to constant exposure to high torque and loads toughness, compressive durability and light weight of joint parts are crucial factors for biped walking humanoid robot parts. When polymer ...transmission parts are used for the manufacture of humanoid robot joint, wear becomes an important factor in terms of transmission error (backlash) between the input and output axes, ex. between the motor and the robot's leg joint. In such joint system, a polymer bushes is directly connected to a cam plate, playing an important role in the robot's movement ability. In this work, the influence of wear of reinforced poly-ether-ether-ketone (PEEK) polymer bushes in friction against 7075 aluminium alloy cam plates is investigated in order to establish the application possibilities in transmission parts in humanoid robot's joint. The PEEK bush surface conditions as well as the input axis-output axis backlash require close examination, so that efficient systems can be built. Sliding wear tests were performed on bushes under 0-50kgfcm loaded torque while the cam plate oscillated. Based on the wear observation, it was found that in a high load range the backlash increased along with number of cycles due to PEEK bush wear. The bush surface roughness also increased during testing. Roughness of PEEK bush surface and the loaded torque for output axis were significantly related to backlash of output axis in robot joint.
In this work, wear of reinforced poly-ether-ether-ketone (PEEK containing PTFE, graphite and carbon fibres) polymer bushes in friction against 7075 aluminium alloy cam plates is investigated in order ...to establish the application possibilities in transmission parts in humanoid robot joints. The PEEK bush surface conditions as well as the input axis-output axis transmission error (backlash) require close examination. Sliding wear tests were performed on bushes under 900 kgfcm loaded torque, while the cam plate oscillated. Based on the wear observation, it was found that PEEK wear fragments in the interface between PEEK bush and aluminium alloy cam plate formed a PEEK film.
An innovative type of one-point rolling contact fatigue (RCF) machine was developed in order to investigate crack initiation and propagation in metals. The microstructural changes and propagation of ...subsurface cracks during rolling contact in specimens tested by using the new device were studied by laser confocal microscope and X-ray diffraction. It was shown that this new method presents several important advantages compared to the conventional thrust type RCF machines.
