A robot comprising: an articulated arm; and a base unit to which the articulated arm is operably coupled, the base unit comprising: a base; a rotating portion; an actuator configured to rotate the rotating portion about a first axis, wherein the actuator comprises a body attached to the rotating portion and an output shaft protruding from the body, wherein the body comprises a motor and a speed reducer configured to transmit a rotation of the motor to the output shaft to rotate the output shaft about the first axis, wherein the output shaft, the speed reducer, and the motor are aligned along the first axis, and wherein the output shaft passes through the rotating portion and is attached to the base; an arm connector located at a first portion of the rotating portion, wherein the articulated arm is connected to the arm connector to swing about a second axis; and a rib straddling the actuator in a plane including the first axis and connecting the arm connector to a second portion of the rotating portion, wherein the actuator is located between the first portion and the second portion of the rotating portion. an articulated arm; and a base unit to which the articulated arm is operably coupled, the base unit comprising: a base; a rotating portion; an actuator configured to rotate the rotating portion about a first axis, wherein the actuator comprises a body attached to the rotating portion and an output shaft protruding from the body, wherein the body comprises a motor and a speed reducer configured to transmit a rotation of the motor to the output shaft to rotate the output shaft about the first axis, wherein the output shaft, the speed reducer, and the motor are aligned along the first axis, and wherein the output shaft passes through the rotating portion and is attached to the base; an arm connector located at a first portion of the rotating portion, wherein the articulated arm is connected to the arm connector to swing about a second axis; and a rib straddling the actuator in a plane including the first axis and connecting the arm connector to a second portion of the rotating portion, wherein the actuator is located between the first portion and the second portion of the rotating portion. a base; a rotating portion; an actuator configured to rotate the rotating portion about a first axis, wherein the actuator comprises a body attached to the rotating portion and an output shaft protruding from the body, wherein the body comprises a motor and a speed reducer configured to transmit a rotation of the motor to the output shaft to rotate the output shaft about the first axis, wherein the output shaft, the speed reducer, and the motor are aligned along the first axis, and wherein the output shaft passes through the rotating portion and is attached to the base; an arm connector located at a first portion of the rotating portion, wherein the articulated arm is connected to the arm connector to swing about a second axis; and a rib straddling the actuator in a plane including the first axis and connecting the arm connector to a second portion of the rotating portion, wherein the actuator is located between the first portion and the second portion of the rotating portion.